Talking with people who own the game, watching WNF, watching YouTube combo clips and matches, reading about the game...I'm pretty darn sure there are some good arguments for not liking the game.
From the looks of it, if you take the game seriously and want to approach it as a competitive fighter, it's pretty easy to get upset at the game. I'm not planning to put several hundred hours in the game or play the game seriously like I did with SFIV/SSFIV, and hopefully that means I'll just have a lot of fun playing friends...but I've already heard enough to have a good idea of why people wouldn't like the game.
I guess it might be easy to get upset, but I am a veteran of MvC2, and a hardcore one at that. If we're talking imbalance, then that game is the poster-child. Yet somehow, people managed to play professionally and enjoyed it.
My point is that people don't like it for the imbalance, but compared to MvC2, there's none there. Also, Peteer, are you a professional at fighting games? The inputs might be simple, but the combos aren't the easiest thing to pull off. I'll also point out that only one character has an infinite in the entire game, and that same character has an infinite in all three editions of SFIV, a game which you seem to revere. Justin Wong at first didn't like the game, but you can see he came around. I'm confident in the future of the game, and with additional editions inevitably being released, I'm sure the rough patches will be ironed out (i.e. fucking Sentinel!). I have personally played at a very high level of MvC2, and I know that despite a fighting game's imbalance, it's very rare to have something truly game-breaking. There's an article on Shoryuken about this I'd like to link. Read this shit, yo.
http://shoryuken.com/content/only-problem-mvc3-you-3694/
Brain I've owned the game since the 02/17/11 and yes there are 100% combo's in this game with the stock 1 meter. Ofcourse, they do not work on the Big 4 (hulk/thor/sent/haggar) who have 1,200,000hp. For your reference here is a link to Trag13's youtube channel where you can find some ver simple 100% setups.
http://www.youtube.com/user/trag13
As for Infinites and comparison to SFIV. Akuma's infinite loop in SFIV is character specific and utilizes 1 frame links. In MvC3 it is a up.Fr Tatsu now there is nothing wrong with this as im sure it is probably also char specific but it is indeed not the only infinite in the game. As you are a reader of shoryuken.com i hope you take a moment and look at the multiple setups by desk for chunli's infinites which 1 requires only D.m. in SFIV to pull off the 1 infinite in the game requires insane execution and i for one have not seen it done in any tourney to date and have been unable to complete even 3 loops with Hk>lp. I agree MvC3 is not a bad game it is highly entertaining but the level of online play thus far is basically keep away and rudimentary zoning which is not difficult to counter but incredibly boring to play against.
Generally speaking after reading the linked article and being a avid SC2 player and SC1 vet i can definitely compare MvC3 at this stage as the oh so upsetting, rage inducing(upvote if you catch the reference), extremely "cheap" Zergling 4-pool and SC2 6pool strategies. Ranked matches will show you some of the most cheeze heavy builds as all players are new they are hoping to get out of their destined rank early by mastering the frowned upon aspects of the game. The only bad thing about this is there is alot!