I built a house in SEMass and we used the warmboard system.
The initial and subsequent contact with the Warmboard people was very positive. The product delivery, plans and layout went very smoothly. We had about 1950 sq ft and the total delivered cost was  around $14500.
Installation was easy really - just use the line up tool. We only had a few small pieces left over, which I later used when we had a little extra room upstairs to heat.
The builders were extremely impressed with the rigidity of the subfloor. It is 1 1/8" thick!!
Putting the pipe in was cumbersome but I worked out a system using a 5 gallon bucket and 2" PVC pipe (thru the bottom and lid) placed between studs, which with suitable modifications to allow it to spin seemed to work just fine. I used 500' pipe, which made for a bit of waste as the runs were between 190' and 280'.
I was able to delay about 1/2 of the pipe installation until we were fully enclosed.
One issue I had was that the plans showed ( and because this was our first go round) a ground floor location for the manifold. Having a basement I would put them down there next time.
I will cover the warmboard next time during construction. The drywall guys nicked the pipe in 2 locations and somwthing fell and crushed the pipe ( an air gun I guess). Having some cheap 1/4 or 3/8 plywood will make me feel better next time.
As well, despite being very careful and really trying, the plumber cut it once and the electrician once as well.
I made repairs by cutting the pipe, drilling down into the subfloor and joining the pipe down there. But you have to use 2 connectors because the cut pipe naturally doesn't meet underneath the subfloor. I use one of those diamond shaped bits - 7/8" I think on a 18" extension to drill the holes. You start vertical and just go down to as horizontal as you can. Cleaned the hole with a grinder and half round file.I took massive pictures of the studs and warmboard so we would know where every thing was.
We covered with both tile (laid over tileboard) over the warmboard, and solid hickory. The wood acclimated for about 2 months while the warmboard was heating the house. Upstairs we have put 7/16 underlayment over the warmboard to eventually cover with carpet.
Installing the hickory was the fun part!!!!!
I had to for visual effect run the hickory parallel with the piping. This meant that you had a really good indicator every 12" whether you were keeping straight ( important as the open plan left us with a 30' long room). Also you had to be really sure where the nail was going. So when a strip couldn't be nailed, I glued it and relied on the next one to hold it until the glue sets. It seems to be working out just fine. Upstairs I installed a little bit across the pipes and it was much easier.
We have installed a 50000 btu Peerless Purefire boiler. We didn't have a frigid winter but even without any covering the house was just plain delightful.
We used the visual indicators on each loop at the manifold to balance the flow. During peak all on performance all returns seem at about the same temp. No instruments to verify. Those visual dials are too cloudy now to use. The gas bill was around $200/month. The Peerless boiler has a habit of stopping due to an ignition lock - it so far has needed a hard power off reset to restart. We will investigate further.
DHW is from a Bosch tankless, which takes a full 45 secs to get HW to the faucet. Maybe this is normal. It is only about 20' of piping to the faucet.
We are out of winter now and all the flooring is laid. Waiting til next winter to see how it goes.
We use a honeywell control unit that talks to the 3 thermostats. It operates the zone valves, but then talks to the Taco circulator/mixer whiccccch in turn tals to the boiler.
Under full steam the boiler maintains 140, and the target temp has been 95 at the Taco to send to the manifolds. 
It seems the returning water from the pipes mixes with the output from the boiler before it has the option of returning to the pipes or going back into the boiler. This doesn't seem right. I understand the boiler has to have a recirculation built in. Will investigate
Well thats it
This is a great product and I will absolutely use it on the next house. 

Just curious but what drove the decision to go with the Bosch tankless instead of an indirect-fired tank running off the condensing Peerless?

45 seconds is a RIDICULOUS amount of time for getting hot water through 20' of plumbing and not normal. Did you time it? How many gallons do you draw before the hot water arrives? If it's having problems detecting flow or isn't igniting quickly there could be something wrong with the unit, or the installation. At 2gpm flow (not a gusher) and a 5 second ignition delay you should should be getting hot water at the tap in under 20 seconds. Most electronic-ignition tankless units fire up and stabilize to temp in under 5 seconds, but I've not messed with the newer versions of the Bosch (some of the older ones were pretty crummy, but not all.) I lived for 15 years with a cheap atmospheric-drafted E.L.M. tankless (the company was later acquired by Bosch), and it never took more than ~15 seconds to get through a 35-40' combination of 1/2" & 3/4" plumbing to the shower at ~2gpm. Something isn't quite right here. If there's a HW tap within easy sight or earshot of the unit, time how long the water flows before it lights up. (This may be easier if you have somebody next to the unit with a watch telling you when to open the tap.)

A schematic of the boiler/manifold/radiation plumbing would be useful. It shouldn't take 140F boiler output to deliver 95F water to the radiation. Efficiency will suffer significantly if the water entering the boiler is over 125F, and it should be possible to set it up to return sub-100F water most of the time, only hitting 120F on the absolute coldest of nights (which face it, aren't really very cold in SE MA, very rarely sub-0F or even sub-10F this season.)

Did you consider engineered wood floors? If so, what lead you to choose solid?

Dana is right again;

the tankless was a waste of time and money (as is so often the case). You had only to add an indirect and voila! perfect water heater (more hot water, lower operating cost and longer service-free life). As for ignition problems with your ModCon; nearly all are self-induced - either from pour installation or neglect.

The Surefire has built-in outdoor reset so mixing for a single temperature radiant floor system is counter-productive as Dana suggests.

Professional design would have put the floor and boiler to much better use. But half-right is better than nothing.

Hey, thanks everybody for their input. In no particular order -
Tried solid wood because had never done it before. The solid pre-f hickory from Home Depot was a great price. Will use enginered next time as the hickory has cupped despite almost 3 months acclimating. It started to cup during the summer.

The hot water takes next to no time to get to the bath/shower, but just turning on these new low flow fixtures in the sink or bathroom and that is the 45 secs. Just physics I guess.

System was installed by a pro, but not designed by one. We just thought a 50000btu boiler wouldn't do DHW. Wrong I see.

The boiler was installed incorrectly as it turns out. I had to change the in/out on the TACO and the return/supply sensors were on the wrong pipes. So now at 130 output on the boiler I maintain 98 from the TACO to the floor and 88 (Delta T setting 10) floor return to the TACO. I think the boiler could be set lower, but would it not then work hard enough causing longevity issues? The boiler seems to hum alomg at 50%. House is beautiful inside, couldn't be better. We are 'frugal', so run at 69 with a nightime setback of 5. It only takes 2-3 hrs to get back to 69 in the morning. Would appreciate input

Having a major problem on windy days as the boiler goes into lockout needing hard reset. Using the correct Stainless Steel Vent Termination Kit about 18-24" off the ground. The exhaust is the open one with the wire grid to stop critters I guess. The intake is behind the plate.
Needs some type of wind protection, but need help here. If it would work, making the exhaust the intake and vice versa would protect the system from wind. Assuming the wind is acting on the current exhaust causing the lockout. It is quite windy here on Cape Cod. Next time we are having a real windy day I'm going to lean the wheelbarrow against it. Plenty of room to exhaust and it just might protect it.

Lessons learned: use engineered floor and get professional design input next time. The pro input will be money very well spent.