It is almost impossible for stealth characters to worse than they were in Oblivion. It was the only archetype I didn't play.
I'm at level 32 with my first stealth marksman character. It's challenging early on but very doable and a lot of fun. In fact, it may be overpowered once you hit sneak 100 and start putting triple-damage potions on your arrows.
Given how stealth has gradually improved in the TES games (and in Fallout 3), I have no doubt it's going to be brilliant in Skyrim.