Hello,
This morning, I've posted a short review of GCC 4.0, comparing it to the 3.4.3 on a number of real-world benchmarks (LAME, POV-Ray, the Linux kernel, and SciMark2). You'll find the results here:
http://www.coyotegulch.com/reviews/gcc4/index.html
Also, I've posted Acovea analysis for GCC 4.0 on the Opteron and Pentium 4:
http://www.coyotegulch.com/products/acovea/aco5k8gcc40.html
As always, I look forward to considered comments.
..Scott