I've used no$gba a bit in the past. Pretty impressive. This emulator emulates the system as exactly as possible, so the compatibility is super high, even on those wonky games that VBA may never run quite right. As mentioned, the speed is pretty darn good too. I still wouldn't recommend it to typical gamers who are looking for the best overall gaming experience, but if you need that compatibility to run something that is off, or want to test homebrew software for compatibility with a REAL gba, no$gba is the way to go. It seems to slowly be gaining DS support which rocks. From what I understand, it also has link support (i.e. emulates 2 GBAs on the same computer) which is really cool.