Yah, I had used O&O for almost a year on my previous Vista install, seemed to work on just one drive.
I did the offline defrag in O&O, after doing so, "check drive" found a chkdsk error. There wasn't an error before, but now there is after O&O just defragged the files it was supposed to optimize. Go figure.
Anyway, doing a trial of Perfect Disk right now. Seems to work better...at least it gives me peace of mind right now. Perfect Disk seems to leave a lot of chunks of free space, as opposed to a few large chunks. I thought it was supposed to optimize that?
Gonna try Diskeeper on next defrag run.