I owned one prior to my current supra. Mine was fine, but there are issues to watch for.
The UK spec ones are obviously exposed to road salt more so than imports, so they tend to go rotten. Honda thought it'd be a good idea to fit rubber lips on the arch lips, these only serve to hold crap between the rubber and the metal, causing patches of rust to appear. I had to remove all the rubber strips, treat the rust and respray, I ended up removing the rear end and sorting out all the rust that had accumulated behind the bumper and trims. My supra on the flip side, although older, had no rust at all.
They also suffer fron water leaks into the boot. you can't see it on first inspection because the bottom of the boot floor carpet is rubberised which masks the leak. Lifting the carpet revealed a stagnant pool in the well. This is sorted by removing the vent and siliconing the area around it.
The clipers are also renowned for sticking, which 3 of the 4 of mine did within weeks of getting the car. EBC carried out a full refurb for £400 for all 4
Someone has already mentioned the sticking suspension bolts, this is one of the most crucial things to ask for and check when buying. The geo needs setting on the s2000 every 12 months, if not, the car becomes undrivable. The way to keep it good is to have the bolts copperslipped when setting the geo. If this has never been done, expect to fork out for all new arms, which is major spondoolage.
The engines are great, but they're not faultless. They are known to consume serious amounts of oil in varying quantities. It's not so much a problem if you keep an eye on the level, but letting one run dry is obviously catastrophic. The engines are generally known to last around 130k before they die.
The roof mechanism can knock like a bitch, replacing the latches with hardtop latches (yes they work with the soft top) sorts the problem.
Here's my old one once finished.