I've been um... debating this on Facebook

I dont see how its a bad thing. If they make more Watchmen stuff and it sucks, then the original book (which will stand alone if for no other reason than it predates everything else by 20 years) will still be the awesome work it is.
But the world and characters created were rich ones and the story does, by necessity, jump forwards a lot. So why not a 6 issue mini showing The Minutemen at their prime?
Its the kind of project they'll only put their best on. Why not let them have a chance to tell a story using these characters? I know Moore would kick off, but he's gotten enough play from other peoples creations. Why not let the next generation of writers build on his stuff.
Dont see how it could dilute the original any more than you could say a bad Dredd story (cant think of one, but there must have been one dud) spoils the Cursed Earth.
As good as they are, they are only comic book characters. Comic book characters need to have stories told.