Ah but all your points should also have applied to Maemo on the N900.. and what did we get.. 2 or maybe 3 firmware updates that didn't really bring anything new. So the track record doesn't really support what you are saying..
The UI for any MeeGo device would have to be very snappy to compete... and if there really is a device being released, i really hope it can compete.. I wouldn't take moving to WP7 lightly..