Have you considered the Fuji645Zi? - for fast paced medium format its got no be near perfect. Autofocus, autoexposure (with full manual override), up to 32 pics per roll (on 220, 16 on 120), motor drive, and zoom lens. It's bascially a compact that just happens to take roll film - loads of fun.

They're light enough to throw around, and best of all they're CHEAP! Sell the prism and winder on the hassey and you'll have enough to buy one, with change left over. There are a few compromises, but at the price you can keep the heavy kit for formal stuff.

Ian