Yes, I participated in a trial for fibroid tumors. they were testing a drug vs placebo to see if the drug would reduce the size of the tumors. I felt very good about my experience. I always said that the paper work involved with adverse reactions keeps the researchers/doctors and staff on their toes so they don't have to do adverse reaction reports.
I worked at NIH for a few years so I'm familiar with clinical trials.
A few things to keep in mind:
Who is offering the trial?
What stage is the trial in?
Is the drug already on the market for something else? Or is a completely brand new drug?
What type of medical support will they offer? (just in case you do have serious side effects)
Some phases are testing a placebo vs the test drug, so you may not actually get the drug they are testing.
These are links about NIH clinical trials, but the basic info is good:
http://clinicalcenter.nih.gov/partic...qaboutcs.shtml
http://clinicalcenter.nih.gov/partic...f/partners.pdf