Well, I'm glad it's working out for you . . . not so much for me.
I'm running (or trying to run) SQL2K8 on W2K3 SP2. I know SQL2005 works with Mount Points on W2K3 because I've got it in a three way active/active/active cluster.
But for W2K8? No. Just a disappointment.
The problem was in set up. I created the standard 1GB parent drive, and the dependent volumes, but when I got to the installation dialog where I could assign the temp/log/data devices, I got errors. I was told, when I requested the sql files be created on the mount points, that my suggested path was either malformed or not absolute; if I chose a hard path from the root of the parent drive, I was told the drive wasn't in the cluster.
Here's what I got when I chose a mount point:
"The path \\?\GLOBALROOT\Device\Harddisk5\Partition1\MSSQL.INSTANCE1\MSSQL\DATA\ is malformed or not absolute. Error code 0x84B40000."
When I got chose "e:\mount-point-for-data\mssql.instance1\mssql\data," I was told e: wasn't in the cluster.
A colleague came in and said, "well, assign drive letters to the mounted volumes." So we did that got SQL2K8 to install, but now I'm stuck with the drive letters, which we don't want AND the parent drive. When we open the explorer now we've got TWO pictures of the same volumes.
I tried just deleting the drive letters and that didn't work: SQL couldn't start dependent only on the path.
What a drag.