I think GTA IV will be the first GTA game I purchase for a console.*
I've got every version of GTA for the PC so far, including good old GTA 1 which I used with Glide support on my Voodoo card

I also had it on the PS1, but it was a bit... blocky.
From GTA3 onwards, I've found the PC versions superior. As has been previously mentioned, the extra time between console and PC release always seems to have been used to improve the graphics quite a bit. Also the keyboard and mouse control have always felt perfect to me, not like a console port at all.
I've played on mates PS2 versions, and always felt them to be sluggish, look shocking (compared to PC version) and of course... no mouse and keyboard.
Still, I'm going to have a punt on the console version this time.
I'm hoping the current consoles are powerful enough to do the game justice. From other titles I've seen recently, I do believe this to be the case, so am going to get this for my PS3. Just means I have to get used to using a controller for it, and having to use auto-aim I guess. Would be good if they'd allow mouse and keyboard support, as they did with UT3.
Anyway, if it's poor, for whatever reason, it can always be sold, and the PC version picked up for probably half the price when it comes out!
Damn, all this talk of it, I fancy reinstalling vice city now
V1N.
EDIT: * D'oh! SECOND. Will be the first 3d GTA I've bought for a console, but I did buy GTA1 for PS1 back in the day.