sorry, i was a bit vague :P
speed is important, WP7 is awfully slow.
working features is a must, no bluetooth on WP7 is a killer.
the latest most stable version would be great, i'm still on the pre NODO update for WP7 due to broken stuff,
and no sense, i do not like the little arc thing for calls at the bottom on the screen if thats whats included in sense.