There is a trend in shooters these days to try to be like RPGS - to offer players skill trees and reward levels with new abilities. Sadly, what they are mostly doing is taking what used to be behind the scenes - small percentage increases of stats when you level, and they put it out front like it's an exciting reward.
The REASON why small percentage upgrades USED to be a behind the scenes, is because IT'S NOT FUN. For some reason nowadays, developers think people think it's fun to level and your reward is to assign a 5% increase to your recoil reduction. Blah. They should LOOSE the skill tree from Borderlands - your choices really don't affect the gameplay that much. Instead they should just focus on the LOOT, which is FUN and which DOES affect gameplay.
I should have thought through before getting this game.
It was awesome and fixed problems that made me hate shooters, but the bad graphics and confusing weapons made the time to have fun limited. One thing that would make this game better is making the game different with events based on the person you choose. The customization choices are small. So a good tip for gamers: buy this for a week or two than sell it.