The controller was set to AHCI during the flash. I flashed a brand-new 160GB x25-m, before there was any filesystem on it, on my work machine (an Asus P5N7A-VM). I ran the FW update, rebooted and launched the updater again to verify. The drive still showed the old firmware. I ran the updater a 2nd time, rebooted, booted Windows 7 RC, installed the Toolbox and confirmed the correct FW revision. I did not create a filesystem at this time.
Took the drive home and connected it to an Asus P5Q SE (with AHCI enabled). I did a clean install on Windows 7 Home Premium, manually disabled the defrag tool, and so far (knock on wood), no issues after multiple reboots and a reinstall of Win 7 to clean up a small hardware issue I had (media center remote wouldn't work).