I've never heard any knocks against Yamaha for reliability (unlike HK, or Onkyo to a lesser degree), and I've purchased tons of stuff from J&R and it's always been a pretty pleasant experience. Good to do the legwork on the brand and seller of course, but neither seem to earn much negative feedback.
Though really, is there any real reason to preorder this, or any other upcoming receiver, for that matter? I mean, you're kidding yourself if you think you won't be able pick up this unit for this price fairly easily elsewhere within a couple months of release, and it's the rare receiver that doesn't have some unforeseen minor-to-dealbreaking issue like lip synch, overheating, HDMI video quirk, etc. Not that I'm discouraging early buyers so I can hear their impressions before I fork over my OWN money of course...