I personally know 2 glider pilots who successfully bailed out of tight cockpits after in-flight structural failures. One of which went into a steep spiral dive and the pilot remembers hearing the wings get ripped off before being able to get out. He may have had some cracked ribs, black eyes, a twisted ankle from landing on the side of a mountain, and he had to walk for ~3 hours before rescue crews found him - but he made a full recovery.
I was running the glider contest where this incident happened so I had to coordinate with SAR, and I had to be the one to speak with his wife for the first ~6 hours - when we didn't know if he was alive. It was tough enough to do even with a good outcome; I don't ever want to have to deal with a situation like that which ends in tragedy.
Its cheap insurance, and for a lot of pilots its worked.
But you
do need to maintain your gear and you need to
practice using it (simulate bailouts on the ground, practice looking down to distinguish your belts from your chute buckle, etc). And - as others have stated - if the chute is uncomfortable you're less likely to use it. The good news is that there are a LOT of different styles of parachute out there and you can find one that works for you (see
http://www.softieparachutes.com/parachute-models.html for an example of the different types and shapes of parachute packs)
--Noel
P.S. Someone mentioned Tucker's difficult bailout. Go back and look at what his airplane after impact and tell me you'd rather ride that into the ground than have a "tough" bailout... ;-)