I've been using my Hasselblad in studio and relatively benign location shooting conditions for a year, with no hint of any problem. I don't shoot tethered. I've never had any hint of hissy fits from the camera or back.
If you go for an H3, why not pick up a second hand H1 or H2F plus film back(s) at the same time? Procentre in London have usually have these in their second hand section and the cost is comparable with the cost of an MF lens. That way you do have the film backup option right to hand.
Or, if the shoots where you critically need backup come in reasonably tight batches, hire a second H plus back for the duration.
Or, take a 5D Mk2 as backup. Sure, it isn't up the quality of the H3's, but 21 megapixels with good Canon L series glass on the front (especially primes) is far better than no shots at all from an expensive shoot day. That's what we do for our location shoots, mainly because we already had the Canons lying around from before we acquired the Hasselblad. The only times we've used the backup cameras are where we have split into two shooting units on location to make the best of the place and the models' time.
I don't know what the conditions are like in your shoots, but I'd probably want a backup I could just pick up and use immediately in case of any technical hitch, not something I'd want to change lenses on or backs on in mid-flight. So if it were me I'd go for a complete ready-to-roll backup with lens on the front, even if the lens/camera choice is a little less than ideal (say a H2F with standard 80 mm on the front...) as that minimizes wasted time fiddling around in case something were to go wrong with the primary system.
Cheers, Hywel Phillips
