Eh, I've done a few and they've been mostly okay.  One was for a guy doing time perception (he had a miniseries on PBS about the brain a few years back).  I sat in a tiny, dark room staring at a computer screen doing countdowns over and over.  My task was to say which one was faster.  I got a case of chicken wings and handle of rum with that.
Done a few allergy medication trials.  One was awful and required tons of pill swallowing and checking in every few hours with a cellular Palm pilot.  The other one I just used a nasal spray once a day.  Got 2 HDTVs and a JTAGed Xbox 360 with that money.
Earlier this year, I was strapped into a chair, had a mask molded to my face, no lights, white noise in the ears, and a platform would move in one direction while the image on the screen in front of me moved another.  My task was to use a joystick to move to where I thought a circle had flashed on the screen.  5 hours! That was honestly one of the most traumatic experiences of my life.  They came back and asked if I was interested in doing more sessions!  Only time in my life I've walked away from "free" money.   

Anyway, the $100 I made from that funded booze and chicken wings at ZapCon.  
So, I hope it was worth it, Mike.... and Ond... and TacoTownCharlie....and Arroyo... and Opt2Not.... and Nephasth...  and all you other ---daisies--- that ate 10lbs of my chicken wings.
Did a chikungunya vaccine trial that bought my plane ticket to Zapcon...
Lately I've been doing a flu study.  Seasonal shot plus an amplifier to see if it would be more effective.  $600, so that's been nice.