Here's some well known problems:
ISC motor goes bad (causes idle surge, where car idles erratic)
Hatch struts give out (I've replaced a pair on every DSM I've owned)
Burns oil (115k, mine burns very little)
Cigarette lighter doesn't work very well
Sunroof rattles/hatch rattles
Thrust Bearing Failure (aka crankwalk, happens most to 95 and up Eclipse/Talon Turbos, believed to be caused by manufacturing defects in a batch of engines), which can be checked by removing the oilpan and measuring the play in the crank...usually happens around 70k miles from what I hear but my car never got it.
If you're really interested in buying a DSM there's a wealth of information available to the community
here.
I hope you don't let the bad things you hear deter you from driving one, they're fun cars to drive
I have a pic of mine under my profile....