Finally got one... pretty happy with it so far. The calibration mic worked nicely and setting up the S-Air rear speakers was easy enough. Keep in mind that if you plan to buy the wireless rear speaker module (WAHT-SA10), you also need to buy the S-Air adapter (EZW-T100). Together, they run about $200, which is basically the price difference between this unit and the 500w. Also note the S-Air adapter adds about 2" of depth to the unit.
I'm using Sony's mp3 streamer (TDM-NC1) from a previous purchase. Ideally, it'd be nice if this unit had a second DM port, since a lot of people apparently have Ipods, but it's not a big deal to unplug one accessory and plug in another, if needed.
Music sounds great. The sub provides plenty of bass, and Sony doesn't disappoint in offering a variety of sound modes. The lone optical input is being utilized for my cable box, which also sounds good with the digital decoding.
I was a little disappointed this unit didn't ship with Wi-Fi for BD Live. I'm guessing Sony reached a limit on features in maintaining their price point. I don't use BD Live that much, but may end up springing for another WAP at some point - unless the mp3 streamer can be used as a bridge.
Also if you buy this system, try to find a usb drive without a light. Or wrap its light in electrical tape. It's a little distracting to see an orange light blinking behind the unit during movies.