It's really excellent. Well worth buying even just to finish a run with each character then quit. They all have unique mechanics and cool builds you can make that are pretty game breaking. It does have daily challenges and an ascension system which makes things harder if you want more.
While you're finishing Oblivion, I haven't even started Skyrim 😂! I'm 40hrs into The Witcher 3 and have a bunch of other RPGs/JRPGs/Shooters to play after that.