Im a BJJ brown belt and the original poster nails it.
MMA filtered down the list of what really works and it looks like this:
BJJ
Muay Thai
Wrestling
Boxing
Full contact kick boxing - the real stuff like K1
Some Judo - less effective without the Kimono in the ring
Sambo
Here is a list of BJJ versus videos
http://www.jiujitsuforums.com/wiki/Jiu_Jitsu_Versus_Videos
You will see an occasional technique used from some other styles once in a blue moon, but they are the exception.
The moment you hear a master from a style claim he doesnt fight in MMA because X, Y, Z, you know he is full of shit. His style is "too deadly". MMA has "too many rules" If they would allow my deadly throat strikes and eye gouges, I would dominate in MMA. They are full of crap and scared. If a few dirty techniques makes the entire difference in your style of fighting, then your style sucks. Anyone in any style can use these techniques and since they cant really be practiced on live opponents, they so called masters of dirty techniques are no better at them than anyone else.
If you can train only one style though, BJJ is proven to beat all the others most of the time. Pure strikers lose against grapplers 99% of the time.
I was a black belt in 3 arts before I started BJJ and all the BJJ white belts kicked my ass. It was a rude awakening to say the least.