I've played it for hundreds, and quite possible in excess of a thousand hours on PS3. That means the purely unmodded, Bethesda intended, glitchtastic, and bug infested version. While it has major issues, some of which split it's community right down the middle (leveled enemies), it's without a doubt the best value for money game I have ever bought, one the very best RPGs (in the top 3), and a gaming experience that CANNOT be forsaken. Similarly I'd recommend Morrowind. The two should only get you back £20, especially if you get Oblivion GOTY for PS3. The other versions come to more for some private lunacy derived reasoning on game retailers part. Especially given how easy it is to pirate.
While I'm at it, I may as well say, if you haven't played it, Fallout 3. But you probably have. Still, such a great game.