Had 2 test rides of the GTPRO , loved it and ordered one.
Vibes are not that bad. Bike reviews are over-stating the issue. The new engine isn't as smooth as the old one but the vibes are tolerable. I decided I could live with them (and I hate tingley vibes) .
The mpg from a mix of motorway cruising, scratching around the twisties, and town work was just over 55mpg. Same as my GS.
The engine is more punchy and sounds better, plus the bike feels light so is more flickable. The brakes are sharper, and the ergonomics and comfort are good too - bars felt a tad closer than the 800 and the screen worked (hooray!).
The quick-shifter is an absolute delight. Once tried, you wont want to go back.
IMO, these are all worthy changes over the 800 and make it feel a different bike. It does it for me at least.