A couple of sites have posted reviews of the quad-core variety of Intel's Xeon processors, which were introduced today. The quad-core Xeon's previously went by the code name of "Clovertown," & the reviews are of the Xeon 5300 series. You can find one here, at Phoronix, & one over here, at the TechReport. Anandtech pitted a quad-core Xeon rig against a quad-opteron rig in their look here.

Check out Intel's press release here. They even launched a website dedicated to their quad-core chips, which I find a bit overkill, but I guess ya gotta convince CTO's somehow...