(The following are brief minor-spoiler comments by me)
I still love those Minions - they're like incomprehensible, PG versions of Beavis and Butt-head - but the rest of DM2 is awfully thin gruel indeed. The first film's main plot was actually reasonably original - two supervillains, both with arsenals greater than that of Wile E. Coyote, competing to steal the moon...with a wrench thrown into the works when one of them has the hare-brained idea to adopt kids so they can sell his rival cookie robots. Gru (Steve Carell) was an aggressive prankster, but his rival Vector (Jason Segel) was a genuine jerk who deserved comeuppance.
In the sequel, Gru's become a blandly nice guy, and his arch enemy's plan to make animals into monsters is more goofy than mean. It also relies on the hoariest plot you've seen countless times before - Gru must go undercover as a normal person to try and flush out the bad guy; in doing so, he falls for his female partner. The three girls get nothing to do, save a romantic subplot that abruptly ends with no consequence.
Benjamin Bratt does a passable Tony Montana parody, and isn't as bad a fill-in for Al Pacino as you might expect, but the character's just not enough to be a worthy villain. Yes, the Minions rule, and I look forward to their spin-off movie. But I need to care about Gru, and I don't.
On the other hand, I plan on seeing The Lone Ranger a second time.
Some of you have had a chance to see one or both by now. Let us know what you thought in comments below.