Three words: Best game ever.
For those who got lost in Morrowind, Oblivion is much more story driven. You can't really miss the main quest this time and it's more action packed. You still have all the freedom you want and you can still chose to begin the main quest whenever you want.
The side quests for the guilds are really good too. What's fun is that it's not just go kill someone or go fetch this and that, bring it back and forget about it. There's variety and there is a story behind it. I finished the thieves missions (excellent ending which somewhat reminded me the Thief 3 gameplay), did a few fighters missions and I'm pretty advanced in the Dark Brotherhood quests (if you don't mind killing innocent npcs, the Dark Brotherhood quests are very well done - you can even convince npcs to turn on each other and do the killing for you in one "Agatha Christie" style mission - and the dialogues are hilarious. If you accomplish your missions by the letter, you also get kick ass rewards). I still have to do the mages quests but I've been expelled for murder and horse theft just after joining...
I also agree with T7: there is no need to have played any other TES game before playing Oblivion. The only thing it brings is that you are able to recognize some references that are more like Easter eggs than anything else. Per example, there are some conversations between npcs in the street that refer to what happen to the Nerevarine, you can also come across a book that tells what happened to Jiub (the prisoner on the boat when you begin Morrowind), Crassius' Curio "The Lusty Argonian Maid" play made its way to Cyrodil (the book is everywhere)
. If you never played Morrowind, these things won't attract your attention and you won't be missing anything.
The game is also very stable. I did not encountered any bugs so far. The only thing is that it draws a lot of juice from my video card (x850xt) at high settings. The card runs a lot hotter than it does normally.