Sorry to be a buzzkill, but I think the other excellent comments are already leading you down this path: VM snapshots, no matter if you're using Hyper-V or VMware or something else, are not supported by Microsoft in SharePoint farms. If you've got a multi-server SharePoint farm, VM snapshots (especially over time) will lead inconsistencies between your snapshots, something you simply can't have if you're relying on them as a DR solution. For more information, I'd recommend taking a look at the first in an excellent series on SharePoint and Virtualization at the MS UK SharePoint's team blog: http://blogs.msdn.com/uksharepoint/archive/2009/02/26/virtualizing-sharepoint-series-introduction.aspx and the links provided in it.
Basically, the problem is what Christopher is alluding to, but I think its too much of a risk to consider using, especially since Microsoft is taking such a drastic stance on it and not supporting its use.
If your customer has made the investment in the Commvault product, its probably going to offer you a lot more than MS's tools in the way of usability and coverage. If you can't get that working reliably, I'd say you'll need to look at SQL backups of your content dbs, as well as SharePoint backups and backups of the critical files on your WFE (customizations, 12 hive, IIS metabase, INETPUB folder, etc) to get the coverage you need.