I've got one, but haven't installed yet... don't know if i will either. The only time I give my car stik is at night and the air is cool enough already.
The highest knock level I have had at night has been 17 which is nothing. However if you're stupid and crusify your car during a hot day it would benefit your cause a little.
If your car is completly stock the intercooler will make it slower due to the extra meter of piping and the huge volume of the intercooler that has to be filled with boost.
A FMIC will make your car look faster, besides that at this level of performance any el-cheapo or brand name cooler will cool effectively enough for your needs. So yes, they work good.