In my experience, it strikes me that fans are the most passionate, but also the most critical about change, whether it be in sports, television, or pretty much anything else. Many of the arguments against Abrams Trek have been made against TNG when it first aired, get made every time Dr Who switches Doctors, and every time a sports team switches coaches or players.
Generally, it comes down to, "Oh, these changes are terrible and the loss of [insert anything here] will kill the franchise." Yet, as much as I loved TOS or TNG, they were products of their era and by necessity need to change.
With regard to Abrams films in specific, people seem to have two primary problems. 1. The lack of "message" and 2. The "rehashing" of Wrath of Khan in Into Darkness. For me, at least in the first Abrams film, the message was about the crew learning to become their best possible selves. It just wasn't spelled out and hammered at like the "message" in Nemesis. As far as #2 the film struck me as an interesting "what if" idea that Abrams plays with quite a lot (Aka, the alternate universe in Fringe).