I’ve just invested in Pentax medium format.

When I want small and light? Sony 1″ (RX100 and successors).

When I want smallish and fast? APS-C (my choice is Pentax because of superior build-quality compared to Canikon, in-body stabilisation, and weather-proofing when needed).

When I want the best IQ I’m willing to lug and afford, albeit at the sacrifice of speed? Medium format (my choice is again Pentax because of the huge amount of well-priced, high performing glass).

Having said that, MF is still a bit of a trophy system if I’m to be totally honest.

If anyone offered a FF digital with the features I insist on (in-body stabilisation, weather-proofing, high quality body, optical viewfinder, in-built flash for fill when I don’t want to carry an external flash, and fairly compact dimensions), then I’d probably ditch the APS-C and MF and blend them into a FF kit.

DOF control (the more the better) has always been my particular soft-spot, and this post shows how MF isn’t all that much better than FF:

http://www.pentaxforums.com/forums/531863-post7.html

However, Canon and Nikon can’t fight a MF (and ultimate IQ) battle as well as Pentax can, so expect Ricoh to put some focus in this area.