I weighed this choice quite a bit and ended up going with the Denon AVR-1910 (same as the 790, more or less). By all accounts, it runs cooler which counts. The easy iPhone/iPod compatibility with no dock weighed in the Pioneer's favor. As well as the fact that Pioneer makes some good Blu-Ray players (I like staying with one vendor, as much as possible) and has better customer service than Denon.
In the end, it seemed like the scale tipped ever so slightly in the AVR-1910's favor. Reviews seem to indicate it plays nicer with a PS3 and does a better job of upconversion.
The Pioneer sounds easier to setup. Though the Denon offers similar auto-config options, just that their manuals are horrid.
I got in on "Name your own price" at 6ave.com last week, but the AVR-1910 is back-ordered a bit. Hoping for delivery next week. Got it for $433 shipped.