Best of the Barcelona vs. Xeon reviews:

AnandTech: http://www.anandtech.com/IT/showdoc.aspx?i=3091
TechTeport: http://www.techreport.com/articles.x/13176/1

Idle power is impressive (p12 in Anandtech),
Barcelona idle: 188W (2P QC, 8x 1GB DDR2)
Clovertown idle: 257W (2P QC, 8x 1GB FBDIMM)
+37%
Barcelona margin more than halved at peak load power (Cinebench)
Barcelona Load: 299.9W
Clovertown Load: 347.3W
+16%