I played for an hour after getting in some Borderlands 2 last night, got to level 10 with three unique socketables, a unique shoulder (sold, was not for my class), and five set pieces. Not counting the numerous magic items I found on top of that.
Progression speed and loot is fantastic. It is everything Diablo 3 was not. It is fast, progression feels real by allow me to make stat and skill point allocations, and I actually want to kill all the enemies I find because they actually drop loot I'm interested in. My brain is totally fucking overloaded with this and Borderlands 2.
I actually find Diablo 3 to have significantly better gameplay mechanics. I think it was a mistake for TL2 to keep the potion system, and D3 having built in character respecs as part of the skill system is genius. But TL2 is more addictive to play due to speed of progression, leveling mechanics, and loot drops.
The only reason I can give TL2 a pass on the leveling mechanics is because I don't plan to play it with an end game focus, which is where player allocated stat systems fail in loot whore games. Once people find optimal equipment builds, it will fall backwards on to optimal stat builds and the entire system becomes weak. But early game? Fucking love it.