Although the scene seems to have much less activity than it did 5 years ago, I just realized how far the emulation of some systems has come. I went back and was messing around with old 32X, n64, and jaguar emus last week, most of which were probably 3+ years old.
My old version of Gens had pretty spotty 32X support, with a lot of games having big glitches or not booting at all. I just tried out Kega and was amazed to see how robust its 32X support is! Every single game I tried worked flawlessly and I couldn't spot any differences between Kega and the actual hardware. Gens had great Sega CD support, but Kega even does the SCD/32X combo. very impressed with how far 32X emus have come.
I had a similiar experience when I downloaded the newest Project Tempest and tried some Jag games. There are still a few bugs, but the games are now very playable. I didn't know so much progress had been made on the system. I played AvP for a couple hours and the only glitches I could find were the automap doesn't work and leaves garbage on the screen and the predator's vision modes don't seem right.
I've always looked down on n64 emulators somewhat because they seem to be mostly just a hodgepodge of different plugins. However, I tried the new Rice video plugin and was again impressed that previously glitchy games like No Mercy work almost prefectly. Looking at the n64 compatibility lists though, there still seems to be a handfull of games that don't work.
I never really suspected emulation on these systems had come so far. Have any other systems made huge progress in the last few years? I think the next on my list to try will be SSF. I remember old reports of it being horribly slow and unplayable with low compatibility, but that sounds like it has changed now.