I'm playing GTA1 again for the first time in a while, I still have a CD copy (PC version). The game itself still plays well enough but after a while the radio soundtrack starts sort of becoming a bit "sticky" - every few seconds there's gaps of silence, although the song still keeps playing (it's not like a stuck record effect). The effect gets worse the longer I play.
And also on the country and western channel (which plays whenever you get into a pickup truck) it doesn't seem to reset itself at the end of the track unless you get out of the vehicle and get back in again (not much of a problem really but still not how it's meant to be working)
Of course I'm playing it on a modern computer (about 2 years old now) with Windows 7 and everything. This means the game menu animations (the key etc.) run about 10x faster than when I played it on a 1990s computer back in the day (but I'm not really bothered about this)