I was never even tempted to buy a DSLR until it had identical quality and handling to a 35mm SLR and in the same format. If I'd wanted a half frame camera at any point in my life I would have bought one. That said I was never a huge fan of 35mm in the first place.
Wouldn't buy a back for a medium format that wasn't full frame or a large format back that wasn't full 5x4 either.
None of this has anything to do with pixels and everything to do with the way a lens behaves - I like the way lenses behave with larger formats and even 35mm was stretching it a bit there.
The viewfinder was a big issue and I couldn't believe the first few DSLRs - is it just me or is seeing what you're photographing in the viewfinder a bit important? I remember the first time I looked through the viewfinder of an OM1 thinking I was looking into the Tardis. When I looked through a DSLR I thought I'd picked up a Zenit E by mistake.