Explain? You'll forgive me if I miss a few points, since it's been almost a year since I played through the game.
As I recall however, I had to go through the INI files and manually edit them to get the game to play comfortably. I had to do this because it was clearly optimized for sluggish console controllers, and had almost any and all options hidden from the user... again, for the console kiddies' sakes.
-The mouse look is terribly sluggish, even with sensitivity jacked all the way up. You can turn off the misplaced mouse smoothing and quickly remedy this.
-Crouch was set up as a toggle. That's dumb. It needs a button to be held down, just like aiming and zooming would.
-My scroll wheel wasn't recognized in text boxes by the developers.
-The FOV was much too small.
-Depending on preference, v-sync could be turned on or off.
These are things that shouldn't be problems to begin with in a PC game. But in this case, Gearbox went the extra mile and excluded even the options from the menus, because console gamers can't handle options I suppose. Unfortunately, there are plenty of things in the game that feel wrong that can't easily be edited away: floaty air physics, huge text and menus, etc. I won't count the abysmally repetitive nature of the game, since that's not a PC specific flaw.
The game can be fun with some friends. It was definitely worth playing, I just wish I hadn't be forced to dig through the system files and fix the developer's laziness to enjoy it. Given how repetitive the gameplay was though, I don't think I would have paid the full price for it in hindsight.