The problem has -not- been resolved. I had SP1 uninstalled on a machine to troubleshoot another problem so I ran the ATTO test which gave me the usual bad write speeds on basic disks. I just installed SP1 and ran the test again, and have the same results.
My test read results are also showing 15-20 MB/sec slower than before SP1 in ATTO, however, the speeds show the same in HD Tach, so I don't know what's up. 🙁