HI Brendon,
The release was pulled due issues with snapmirror and hyper-v lun enumeration.
1) SDW 6.3.1 does not recognize SnapMirror relationship for LUNs in a Qtree
2) SDW 6.3.1 does not enumerate Hyper-V shared LUNs ina non-CSV (Clustered Shared Volume) configuration.
Recommendation: If you have already installed SDW 6.3.1 and are having issues with these specific issues then customers are advised to downgrade to SD 6.3P2.
http://now.netapp.com/NOW/download/software/snapdrive_win/6.3P2/
For all other situations: SDW 6.2.1 is GA and SDW 6.3 is FCS and available on the NOW site.