Having the Yamaha RX-A1000 for a while now and having had the Pioneer SC-1522 for a little over a month now, here are my thoughts in a nutshell: the Pioneer is definitely the best bargain right now. However, if the prices on the Pioneer and the Yammy were equal or close, I'd stick with the Yammy. It is NOT worth $1600 or so when a nearly equivalent Pioneer is $599.
The Yamaha was way easier to set up and had a more natural sound out of the box. I also prefer Yamaha's snappy, easy to get around overlay GUI. The Pioneer has the ability to sound great, but it took a lot of work for me to get it right. Way more than the Yamaha. Also, Pioneer's specific labeling of the HDMI ports drove me nuts at first. But now that I've adjusted to the quirks, I'm finally starting to enjoy it. The Pioneer definitely has more bells and whistles than the Yamaha too.
Can you get the Yamaha for $800 or less? Grab it. (Good luck with that.) Otherwise the Pioneer is a great deal, if you can get used to the quirks.