Overrated;
Laverda Mirage. Top heavy & not as reliable as I'd been led to believe.
Honda 400/4. Fussy.
Ducati MHR. Swopped my Commando with one for an afternoon. He didn't want to return the Commando, I couldn't wait to hand back the keys to the Ducati. Felt slow turning and ponderous compared to the 750 Commando.

Underrated
Kawasaki Z-400 twin. Did 35k on mine, before selling it to a girl who toured round Europe on it. Last seen with 85k on the clock, still going. Probably had done a lot more, as it had the habit of eating speedo cables.
Honda 400N Superdream. Bought one after the 400/4, and it was a much better bike.

Bru