First of all you arer talking about the GOTY or Game of the Year edition. The GOTY will have Shivering Isles and I am almost positive Knights of the Nine.
Yes it is a very good game....if you like that kind of stuff that is. My friend hates anything to do with Oblivion.
You can download several things off XBox LIVE for Oblivion. Both Knights and Isles along with Horse Armor, the Orrery, Wizard's Tower, Vile Lair and Mehrune's Razor. Those are the only things that come to mind though. In truth it would be cheaper to buy the GOTY edition and then get Micro. points for the rest. It would save you 10, maybe $15.
Courtesy of Lycanthrope
Proudly paired with: Blazin Torchic- No longer. He is banned.