I won't argue finicky points about whether the minions are funny or not, it's a purely personal preference, and I think they're an absolute delight.
I will admit I'm skeptical to a full feature length movie with them, chasing bananas and whatnot. Haven't seen the movie yet, I guess I will someday. The reason I'm skeptical is plainly because of past experience. Movies like Shrek and Ice Age are both excellent, well-rounded movies, but their parade of sequels, while still finding them entertaining, have way too much the feeling of a cash-cow, marketed towards younger audiences, with themes befitting them more than anything. I realize these ARE movies made for children, but for example Shrek is laden with themes that will go way over the heads of younger audiences, and while the sequels do that to some extent as well, bwlablbwallbalwablalb.....
I just realized this isn't getting anywhere, because what it all boils down to is that for me, the sequels to the aforementioned movies haven't managed to recapture the spirit of the first movie (in my opinion), and simply just ends up recycling the same old tropes and jokes using the all too familiar themes from the first movie (he's a big scary ogre and it turns out he has feelings, ha ha. That was funny in the first movie because it was unexpected and so on, not funny again unless you properly mix up the formula). One of the things I liked about the first Shrek movie was its fantasy-themed world juxtaposed with themes and ideas from our own reality that gave it its own kind of logical reality, and while the following movies do a good job of expanding on that world, it does the fallacy of making it too familiar.
Anyway it seems I completely lost my way with this post, so I'll try to make a quick ending for it: While the minions are loved by many, me being one of them, this movie smacks way too much of being a cash-cow designed to milk the concept before it grows completely stale and unprofitable, as is the issue with most things that end up being a franchise these days. Despicable Me was perhaps intended as a one-off shot, but it stuck so well to the wall that they decided to expand the concept to make more money off it. I feel sequels often ruin the main character in some way, taking away the extraordinary and making them completely mundane, like the birthday party in the beginning of Despicable Me 2.
I will also say that I was originally not a huge fan of Despicable Me, I mostly enjoyed it because I found the minions entertaining.