I'm coming up on the end. Overall it is clearly the weakest of the three. IMO no one will probably argue that fact. But it is still Borderlands so it is still decent. I feel like the jumping addition was a nice try but an ultimate miss. I feel adding this amount of mobility just makes the level design either restricted or not matter. Z axis is basically a thing of the past since you just need to jump on a few boxes and now you're at the top platform and things like that. Just not a huge fan.
The game is mostly predicated on the storyline missions. They are, by far, the best missions in the game. I can't recall a single side-story mission where I went into a smaller zone to do some stuff then came out the other end with loot. Most side missions are "Go into the giant open zone, do X here, then Y here, then Z here and you're done." They are fairly bland and unimaginative. BL2 had it's fair share of these as well but it also sprinkled in very well thought out side missions. I haven't really encountered them here.
I, like everyone else, play Claptrap. I like the design of the hero very much. Possibly the most fun hero I've played in Borderlands but I admit I have only played 3 (Roland in BL1, Roland-again-guy in BL2, Mechromancer in BL2) so my opinion may be weighted. I like that he doesn't specialize in a single gun. I need to have basically every weapon in my inventory and switch my primary with whatever weapon comes up next on the list to use. It adds a certain amount of diversity but sometimes adds a frustrating amount of randomness. Like if I get shotguns I am an unstoppable killing machine. If I get sniper rifles ... not so much. But I suppose that is the point of the hero. His action skill follows a similar suit where sometimes it will pick the jackpot and wipe the screen and other times I'll get on my faggot bouncing duck.
So like I said. Worse of the three but doesn't deserve all the hate I feel it is getting in the thread.