my wife has some reservations. I LOVE the idea of being free from the electric company but having never lived off grid before, I need some feedback on what to consider. What are some things that maybe aren't common knowledge about going off grid? I know cost can be an issue but that aside, is it more trouble than it's worth? Thanks!

This would depend on where you live, but if you are tied to the grid already ( example: you get your electricity from your utility company ), you may still want to be grid-tied, even if you have a system that will provide you with "24 hour power" ( off-grid ). The reason why is because any electricity that is not being stored in the batteries or used in the house is going to be sent back out to the grid ( net-metering ), and your UP will give you "credit" for what you are back feeding to the grid. However, with solar, every solar needs "backup". For example, before you get solar, your main electrical supply is from the grid ( or the UP "utility provider" ). Therefore, technically, your backup is the grid. The same is true even after you get solar installed. Even though your primary source of power is from solar now ( as an example ), your backup, in this situation, would be the grid.

When considering going "off-grid", you need to also get a backup for this. We set up systems where customers will have a small generator that will act as a backup against the off-grid system. The reason for this is in case there are days where there is not as much sun as "normal", the generator will kick on to help charge the batteries ( for storage ), in those instances where the panels are not generating as much electricity ( due to ambient light ) because of the cloudy or foggy weather ( as an example ).

This is probably the biggest thing that people overlook when setting up off-grid systems. You also want to make sure that you understand how much power you are going to be needing because this will make a difference in deciding what type of battery to use for your install ( due to amperage ). Without knowing how much power you need, this makes it hard to "size" a system. Typically, we would have you fill out a load sheet identifying the loads ( AC & DC ) in the house, so that we could size the system properly, so keep a watch out for that in case you go down that road. Good luck!

It's hard to make it cost effective. Even a natural gas driven generator where you use the electricity and the heat can be marginal (because of capital and maintenance costs).

Have you done the math on this? 

In 6000+HDD climates in areas w/$0.15+/kwh power it's cheaper up front, with a lower net operating cost to go with the 1.2kw Honda/condensing boiler grid-attached combi than it is to go geothermal, provided you're not in a superinsulated or very small house with a pipsqueak heating load.  It's not a huge cost adder for the cogen portion over straight-ahead condensing gas- payback is sub-10 years.  (Replacing a typical 55-60% efficiency high-mass beast of a boiler with one of these has a sub-5 year payback on fuel & power, according to the guy sittin' in the office next to me, who has one in his large suburban Boston home.  It cost him within a couple grand of what another contractor had quoted for just a condensing gas + indirect HW installation.  In his case, it was cheaper even up front to go with the cogen-combi, which made it a no-brainer.)

The VW/LichtBlick grid-attached grid-controlled cogen is even cheaper still, totally wipes out  the power bill, and maintenence is paid for by the utility (LichtBlick.)  This is only useful information if you live in their service district (northern Germany) though. :-)

Doing a gas fired cogen off-grid is somewhat less cost effective, but requires a significant annual heating load, a bunch of thermal storage and some battery banks to make it work well. (Got space for a 1000-2000 gallon well-insulated tank?)  Designing in the right balance of thermal & electric storage as well as generator sizing is very project & location specific, but it's doable.

But fer sher, grid-attached cogeneration is much cheaper, easier & more flexible.  I keep hoping more options will become available the Honda cogen in the US, since it only comes coupled with a boiler ~4x oversized for my design day heat load (above the 12MBH output of the Honda) even at it's minimimal modulated output. The Honda alone could support the well over half of my heating-season thermal requirements if properly buffered, and all of it for 8-9 months out of the year.  I'd do it if they sold it un-bundled, or with the tiniest of condensing boilers, but they don't...   (If your design-day heat load is north of 80KBTU/h, it's worth considering, otherwise not- that sucker is a MONSTER of a boiler for most well-insulated homes.)  The goods from Marathon are similarly oversized for my situation.

Yes, in my case it wasn't worth it. But it may be in other situations and the concept is good.

Depends on your motivations. We just made the jump to our new house, and so we've been off the grid for 2 months roughly. I love it, but it is definitely not a seamless transition. First order of business is switching all heat generating appliances from electricity to propane. Our dryer, stove, oven, and on-demand hot water heater are now all propane. At $1.39/gal, propane costs almost 50% less than grid electricity to generate BTUs, so even though we are paying (an amortized cost) of 20 to 30 cents a Kwhr for our solar electricity, we have converted 75% of our previous 10cent/kwhr electric usage to propane, which is equivalent to 5 cents/kwhr.

Surprises since jumping off the grid: The freaking dishwasher is an energy pig. We have an efficient $1100 Bosch dishwasher, and I don't know what setting they use to get their energy sticker, but must be the lamest setting. With colds and H1N1, you can bet we're not running the dishwasher on the coldest setting. The killer is the electric heating element that heats the incoming hot water to a much higher temperature. I don't dare ask my wife to wash the dishes manually, and I'm not up for it either, so after 2 very cloudy days, its time to run the genny so the dishes can get washed. Another surprise is how much electricity our teenage daughter uses at 5:30 am to run her hairdryer, hair straightener, hair curler, and clothes iron. I knew they use a lot of energy - I just didn't realize how much she uses them before I wake up. There's barely enough Kwhrs to brew a pot of coffee in the morning. :) Auto-defrost on the freezer portion of the fridge/freezer is a pig... on enight I went on a rampage trying to figure out why we were pulling .7Kw and everyone was asleep. Defrost on fridge was the culprit. (our deep freeze is manual defrost and not a problem).

If you have the $, and if you're willing to do without air conditioning on cloudy humid days, I say go for it. Personally, I think the batteryless-gridtie-systems are a fad, since the utility company can (and eventually will) install and operate solar panels in a central location for half the price.

One other thing to note - depending on where you live, you may not be able to get an energy credit from the grid by producing more energy. In the midwest, where I'm located, they will not let anyone sell energy back to the power companies. There is a good reason for this - if power lines are ever down because of a storm (or tornado), they need to know the power is off before workers can be sent out to repair power lines. Otherwise, your home, which is less affected by being off the power grid for a few hours (or days) will still be generating power and sending it through the lines, making it very dangerous for the employees trying to fix it up for everyone else.
One option that I looked into was the Mariah Power Windspire. It probably won't get you completely off the grid, but it's basically a wind turbine that can be set up in a residential area. Check out this web site for some more details: http://www.energysmartcompany.com/page/mariah-power-windspire. Even if you don't go completely off-grid, you can provide yourself with sufficient power from non-grid sources to make your power bill next to nothing. And, as mrsolar mentioned, the power grid can always become your backup system.

All UL-listed grid-tied inverters are supposed to monitor the grid and shut down or disconnect from it when the electric fails. Essentially they are automatic transfer switches. A far greater danger to linemen are homeowners using "suicide cords" to connect their generators to the range or dtyer outlet in their house.