The vibes sound normal. The only way to make sure is to ride someone else's 750. But with modern high revving, super light bike, vibes are just part of the game. Older models used to rubber mount everything they could, where as newer use the engine as a stress member of the frame. There isnt much of anything stopping the vibes.
As for revving faster than a 900RR, well it damn well better! Its a lighter engine, with a much lighter flywheel. Its not a bad thing.. its zingy!