I have been reading about ICF and am thinking about building a home using the technology.   What are the disadvantages to using this technology?   If it is so good why is it not more popular?

My spouse and I had our house built of ICF and have been living in it now for over 5 years. We love it and, so far, haven't encountered any disadvantages. It's very quiet, economical to heat and cool, safer in a storm, and the walls went up in a matter of a few days, much faster than conventional stick-built homes. I have no idea why its not used more, except that we did have some difficulty finding a builder who was willing to try it.

Experience is probably the biggest disadvantage, not trying to sound negative, but there are still quite a few undeveloped areas where ICF is not common or popular, finding the right guy to do the job could be a problem. Many times I have recieved plans from 100's of miles away, people wanted the ICF but cannot locate anyone to complete the job and are considering going another route.

The most talked about "negative" if there is one is cost.  In most areas it costs more than "stick built" would. 

When cost are compared to "stick built" are they comparing walls equivalent in energy performance? or just a code 2x4 wall? What about comparing a Quadlock Plus Plus wall (r-40) to an stick wall (total wall R-40 with equivalent air infiltration rates)? If these wall are remotely close, the ICF wall still has the advantages of strength and durability. Also in an ICF wall has a higher percentage of your dollars in premium materials and a smaller percentage going towards labor. In other words you get more house for the money.

No disadvantages in the energy department with oil at $140 bbl.
No disadvantages in the structural area either. Bomb proof, hurricane proof  construction.

Of course, this costs more ! It very well should :-)

The disadvantages are manufacturers who promote product with outrageous claims about realtime costs, and do little follow up to ensure
their so-called "trained installers" are doing a proper job.
Until manufacturers inspect and perform sign-offs on jobsites, the industry will be open to carpetbaggers and corner-cutters.
The implication that anyone with a little training can be a certified installer is bunk.
 
ICF jobs require more intelligence, and effort in planning and co-ordination from begining to end, than wood frame, period.

Converting wood framers to ICF is a hit and miss scenario, at best.
Different mentality's altogether.
 

Don't forget that R-value is not the only factor in how efficient a wall truly is, although the pink panther would love for us to believe this (and he has done a good job of making most believe that R-value is the biggest and best thing going).  Don't get me wrong, I am all about building with ICF, every one of my foundations is now ICF, the customer doesn't even have a say in it, if they want one of my houses it comes with an ICF foundation.  That said, the biggest disadvantage for ICF in my area is the cost (mainly due to the price of concrete).  It also depends where the house is being built, when you reach -40 for a couple of weeks a year you also lose out on one of ICF greatest benefits - Thermal Mass.  Long story short, the biggest disadvantage to ICF is the cost, and depending on where you live, maybe the extra cost is easier to justify because you can exploit ALL of the benefits of ICF construction.

From my personal experience of using it for the first time, I would say cost is a deterrent mainly because people do not compare wall building costs including insulation and frost walls for the basement.

Another major issue I am encountering currently is geting building permit approval. My ICF system comes with engineering stamps but the city inspector still wants structural load calculations for the pads as this is a 9' basement (also stick built roof and dimesional lumber floor so no loads provided as would be with ). I think he's just being difficult but it's an added and unexpected cost. This issue is presumably due to ICF being a relatively new product and my city being somewhat unfamiliar with its' use.