I'm almost embarrassed to post this but I just spent the day shooting with my new IQ150 on DF+ fw 2.3.1 and ... It seems to have been transformed in terms of usability. Seamless integration between the body and back, and I just noticed that the back now has up to seven bracketing stops as an option (which I don't recall seeing before).
Live view is a real transformer. Totally integrated with the DF+ too in the right modes (well, it was before but now it's usable).
There, I said it, DF+ & IQx50 at least seems like a world of difference to my IQ260 already. Let's see how long the honeymoon lasts