In my opinion, the complaints towards the MMPR movie reboot falls into three categories...
1) The old guard whining about the nostalgia movies overtaking their cinemas: Like Bob mention, its mostly the older critics who are out of touch with the new generations of film-goers. The flux of nostalgia properties like Avengers, TMNT, Transformers, and so on is Hollywood jumping onto the popular bandwagon (aka the "monkey see, monkey do" mentality). Until this trend is no longer viable, which won't be for some time now, they're gonna have to get use to it like everyone else. Turning your nose up towards this rather than trying to understand these franchises and their fan-bases better is only going to make the demise of your respectable position all the more swifter.
2) Gen-X turning their noses up towards Gen-Y's nostalgic properties: This one highlights the severe mental disorder the Internet community tends to have. I know the Internet has a bad habit of being so closed-off with its likes/dislikes that it won't let in any new ideas or experiences. But shouldn't it be more welcoming towards fellow geeks regardless of their tastes? It's almost as bad as attitude the cinema snobs have towards these properties(no relation to Brad Jones). Personally, both parties need a massive prescription of "get the fuck over yourselves" delivered to them in suppository form.
3) The fans of this show fearing it will be the next Michael Bay Transformers: I tend to fall into this category. I watched this show as a teenager and I actually enjoyed it. I like the prospect of a reboot but the lingering doubt that its going to be placed in the hands of total hacks who'll turn it into another grim & gritty piece of garbage scares me to no end. That I understand. We've seen too many properties fall into this trap because of clueless marketing dipshits who would be better off promoting Captain Crunch at the local supermarket instead of mishandling our childhood. Plus the fact that Power Rangers is going through one of its worst seasons is not helping to alleviate our fears.
Right now, its too soon to be overreacting. All we got, news wise, is just an article that just states "Hey! We're making a movie in the near future!" No mention of actors or directors picked for this reboot. We might get more news come San Diego Comic Con later this summer, we might not. We shall see.
I'd personally like to see this movie retain the colorful camp nature while exploring some darker tones like Power Rangers in Space or Power Rangers RPM. Maybe expand on the mythos of the show and offer something new at the same time. I would love to see the movie explore the heroes and villains of the series more deeply. Right now, it has the potential to be a good movie or a bad movie. Nothing has come out to say otherwise. All we can do is wait and hope its gonna be placed in capable hands.
Although, making a public checklist of dos and don'ts for this project wouldn't hurt. ^^;