Oh yeah, I didn't care about the drops between waves either after Knoxx came out, but I bought Underdome just a couple days after it came out and was seriously disappointed about the crappy weapons between waves.
I didn't care about gun drops between waves because you can farm Crawmerax or any chest run over and over and over again.
An extended skill tree, more classes, and the option to play male/female for each one is what I'm looking for. Once you hit 69 you can pretty much have points in every skill.
The collection cheevs sucked ass for Claptrap. I really don't think there's any real way to get them outside of farming Minac. I put at least 40 hours into that DLC and only got the bobblehead one and had to resort to faming Minac.