I hav every little (greater than zero) hands-on experience with it. The thing about such options is that it makes everything very theoretical. They do not deal

I hav every little (greater than zero) hands-on experience with it. The thing about such options is that it makes everything very theoretical. They do not deal with device "geometries", device specific hacks, Fmax targets etc. They might as well be logic simulators of old, just with a friendlier syntax. A very large part of coding for FPGAs is to actually make your design work within very tight hardware limits, at a particular frequency, while satisfying routing contrainsts, very limited RAM, limited number of Fast Multipiers, etc. So while Icarus would be ok when you are learning verilog/vhdl, it doesn't really help you learn any of the practical stuff. To use a bad-car-analogy, its like learning to drive using a driving simulator on your PC, controlled with cursor keys instead of steering wheel. Yeah, I know. I didn't find that funny either :p