Combat was tedious and what really made things worse was that all the environments looked the same. Framerate was bad too, but as long as there isnt a lot of tearing then my TV can compensate for that.
Combat is significantly different. In case you haven't been following there is something called VATS (Vault-Tec Assisted Targeting System). When you see an enemy, you can press a button to go into VATS mode.
When in VATS mode the game is paused. You have time to decide exactly where you want to shoot your target. Head, torso, arms, legs, etc. Depending on the size of the body part and distance to you, you have a percentage of 0 to 100% shown of how likely it is you will hit it. You can queue up several shots in a row using your action points. Number of action points is determined by agility and other perks. When you confirm your actions it goes back into real time mode and executes your shots.
You can also aim shoot freely without VATS too. But you just get more bang for your buck ammo wise if you use VATS. Your action points take a few moments to recharge. So if you have run out of AP but baddies are still bearing down on you usually have not choice but to revert to the free firing.
Regardless of using VATS or free shooting, which part you target has a significant impact depending on the type of human/mutant/animal/robot. Oblivion doesn't have this. For example, if you shoot something in the leg you can cripple it so it can no longer run at you anymore. Or you can shoot the weapon out of enemies hands etc.
Note that enemies who drop their weapons will often pick them right back up again if you give them time to do so. Or they will run to pick up some other fallen comrade's weapon nearby.
Like Oblivion there are weapon skills you can develop so you can improve your performance in a particular weapon type. There are critical hits if you are lucky. And Sneak attacks are always critical hits.
Environment wise it is less varied than Oblivion. It looks consistently like a trash can. Just look at screen shots and decide if you like it or not.
Frame rate is fine.