I still say the display issue is something to at least be cognizant of.
The problem I've always had with iMacs is sort of like those old combo VHS/DVD units; if one thing goes wrong you lose everything.
I can't say the Mac Pro makes sense on a strictly price/performance basis, but there are other things that enter into an equation like the aforementioned losing the use of the entire system in case of a display failure, cooling on the Mac Pro vs. the iMac if you're doing long, complex renders and multi-core throughput and the fact the Mac Pro uses ECC memory and can detect RAM errors the iMac would be clueless of.
Certainly for most the iMac would make more sense, but that's not to say there are not still strong business cases to be made where the Mac Pro is the better option, even today.