I played through all the borderlands games solo for a playthrough and enjoyed it, but the playthroughs with friends were definitely more fun.
Yeah, those games can be really fun w/ other players.
Problem is the usual mess w/ other leveled players, when doing these games. Are all the players on or near the same level? Can you guys sometimes not play together and when you do still be playing enough that when you join back up together, you're still on the same level?
Last thing a player needs is everyone's leveled all over the place - for craps & giggles, say I'm level 2; you're level 35; another guy's level 33; and another guy's say level 20. That's just not fun. Level 2 player is dragging the team down, as that guy is doing probably little damage and will need to get resuscitated all the time.
The other thing is w/ these types of games - when I played Guild Wars 1 way back, my friends were way leveled-up already. And basically, they didn't want to create new char's. But, they tried to drag me along, at my low-level and all. They were decimating everything & I was either being healed or dying all the time. They were doing all the work. This means, I had to do a lot of work on my own to catch up. I wasn't that great at that game, anyways - as I was doing "meh" playing solo. I never really did play too much more...and just basically put the game aside.
Also, since those guys been through the game w/ a few char's already - they always wanted to skip the damn cut-scenes. So, yeah - I was kind of losing out on some of the game's so-called character stuff, story & plot too.