So this is similar to what GR did with DC Adventures years ago - a specific-universe game using M&M rules. That seems like a good idea for me and might bring some additional attention to M&M. Here's a link to the Kickstarter.
Looks like they are doing it as 2 books (rulebook + setting book) plus a GM kit at this point which I would say is perfectly legit as an approach. Steve Kenson is the designer so I am confident it will be decent and live up to the "fully compatible with M&M 3E" statement. They have made their goal now so it's happening for sure.
I will say I'm not a huge Valiant fan - I've tried to get into some of their books before and it never really took but as an M&M supplement in effect I am interested. It mentions they have access to Valiant's art files so it should like like it's supposed to look as well.
There is a free quickstart PDF out on GR's Site and DTRPG too - I will review and post something here soon.