Out of curiosity, I rolled a Bosmer archer in Oblivion last night. I found the gameplay mechanics to be debilitating.
I exited the sewers and immediately set upon the bandit encampment across the water. The first issue I noticed was the enemy AI. One of the bandits noticed me and gave chase while the others merrily went about their business. I was able to dispatch them with never having to take on more than two. Not game-breaking, but somewhat immersion breaking.
I headed back to the city and sold off my loot (the persuasion mini-game remains a cryptic mystery to me). I headed back out to acquire the ring of waterbreathing (Bethesda. . .c'mon, you rendered the primary trait of Argonians worthless in the opening act. . .). Archery and water is a bit of a gamble so I switched to my knife. Apparently, slaughterfish are slippery little guys because I could rarely hit them with the knife and did little to no damage when doing so (yes, I picked "blade" as one of my skills). I ended up drawing them closer to shore where I could pick them off with arrows. Again, not game-breaking just annoying.
What breaks it for me may seem trivial to many of you. I play Skyrim almost exclusively in 3rd-person mode. I'm not sure why, but it is far better for me that way. Only on important archery or magical shots will I resort to 1st-person. In Oblivion, 3rd-person mode is just about worthless. I'm not even sure why they included it. Movement is wonky and you are forced to only view the back of your character. This is what ruined it for me. I can deal with the limited AI and the odd combat, but no usable 3rd-person view was driving me crazy.
Gonna continue to wait for Skyblivion.