In SR3 i loved doing the assassinations. In Sr4, you would go assassinate bouncing question marks or toilets that had superpowers and would bounce around shooting all kinds of crap at you. The whole alien and superpower thing did not appeal to me one bit.
The superpowers are kind of fun to mess around with at first, but quickly become tiresome and repetitive. Kind of like Prototype. There is also no real need for cars since you can speed run and superjump over buildings. Although, killing people with melee moves/Superpowers was fun.
It was a drab, gloomy, lifeless and boring world. Since you're actually in a VR simulation being run by the aliens who invaded earth , it's always dull and gray with a bunch of neon type lightning.
When you wanted to change weapons, the scroll wheel came up and stayed on screen for half a second or so, which was incredibly annoying and took away all the fluidity of the fight.
The missions were boring and repetitive. I just couldn't get into it one little bit. It was basically a SR3 DLC that added aliens, a few new guns, a crappier world and some superpowers.