The final act could have been executed better, but I loved that it was there because it tied the two movies together, although in a very ambiguous way. The first one came out in 2008 and this one clearly takes place closer to the present day (she has what looks to be an iPhone 4 or 5). However, I think it's very possible that the two movies take place contemporaneously in their own universe, given that the first one established in its final shot that the monster fell to earth from space, the monster(s) in the second share some physical similarities to the first, and Howard's references to different stages of an attack. So maybe these two movies and any future ones may be all about pieces from the same event? It's also possible that this one is meant to be a completely stand-alone installment (and it definitely works as such), but it doesn't make much sense to slap the Cloverfield name on it and completely change the film style (away from found footage) if they weren't connected.
I guess all I'm saying is that I loved the ambiguity and that it generated this discussion with the people I saw it with last night.
My biggest complaint was the shitty CGI in the final act.