Experiences seem to be mixed, and I believe X10 has the same potential issues. So if you're using CFLs with X10 and reliability is high, I believe you should be OK with Insteon as well.
Some CFLs cause excessive noise on the powerlines that can interfere with powerline signals. I believe some brands are simply worse than others, and depending on what else is going on in your powerlines it might be too much noise.
I personally have a bunch of CFLs installed, and my signal reliability is very high.