I flew one for a thousand hours or so.
They have about the same fuel burn as a King Air 200, with a wider and taller cabin, much quieter cabin, certainly more comfortable. It goes to FL410, and cruises about 370 TAS. Piaggio likes to say it does more (they say 395, and a bit more than that for the Piaggio Avanti II)...but realistically 370.
It's got no antiskid and it has carbon brakes that aren't very effective when cold, and very effective when hot...there aren't many avanti pilots who haven't flatspotted tires, as a result.
It lands fast for a turboprop...more like Lear speeds. The props do have one big advantage, though. You can hold speed until short final if need be, then get rid of it by coming back to idle; the propellers slow you down in a big hurry. This makes merging with fast traffic at busy metro areas a snap.
It comes with a decent avionics suite and a good autopilot. It's got it's drawbacks, too...but overall not a bad airplane.