I went the more cautious route...
I added a single drive in "test pool" using the getting started wizard, then added all the rest to this pool. I added them, not merge.
This adds all the free space on each drive to the pool, and also removed the assigned drive letters.
I then went back into disk management and reassigned all the drive letters.
I can now see the existing files on the drives, along with the GUID folders that drive bender will use to store the files.
The new drive bender drive was also there, currently empty.
I went all out and lobbed 1.6Tb of movie files onto the newly created bender drive. It coped well enough with this, and as I could still see and monitor the actual disks, it was interesting to watch as drive bender distributed the files evenly amongst the drives, keeping the free space on each around the same. This is why I asked about backups vs file duplication in drive bender.
Currently, while everything else is geared around the old drive letter set up, if I download a gigs worth of stuff directly onto a drive that's in the pool, the stuff is not available on the pool drive, but the pool drive dynamically adjusts its available free space. I'll be running this way while I decide which way I'm going to go with this...
The backups have to come from the virtual drive, which is causing me problems. Other than that, I can see what it's doing, and if I do go wholesale with it, I'll take out the drive letters and just leave myself the one drive bender drive for everything to work off.
It seems a remarkably clever concept, and at $20, not a bad price either.
-marko