CNET has the Sony KDS-R60XBR2 strapped to the ole test bench today. Does the higher price XBR justify its premium over its little brother? Its hard to say but the XBR does have CableCard support, brighter bulb, extra HDMI input and more advanced picture controls. My feeling is that most people wouldn't notice the difference unless both TVs were side by side and they were comparing brightness.
From the article:
The picture quality of the Sony KDS-R60XBR2 is among the best we've seen in a
rear-projection HDTV, although we're not scoring it any higher than that of the
KDS-60A2000 or last year's KDS-R60XBR1 (which has been re-rated to reflect this
review). The XBR2 exhibited excellent black-level performance, superb grayscale
and color decoding accuracy, and very good uniformity across the screen.
Nothing's perfect however, and the Sony did fall short on primary color accuracy
and some video processing issues, namely 2:3 pulldown.