the level cap is a big flaw in the game. there isn't any reason not to let people continue leveling up. Max out all the skills. guns will need to continually be upgraded to keep up with the baddies. you could play it forever. as is there is little reason to continue playing after you hit 50. especially with the nerfed loot.
I pretty much completed the last DLC and didn't even bother with the sidequests. I'm realy burned out on Borderlands in general. It was a great 90 hours though