Microsfot Data Protection Manager delivers continuous data protection for Microsoft Applications & File servers. It was specifically built to protect and recover SQL Server, Microsoft Exchange Server, SharePoint Portal Server, Microsoft Virtual Server, as well as Windows file services through a disk to disk to tape backup strategy. An example of a typical setup can be seen below:
The Continuous Data Protection means that changes are backed up almost as they happen, giving you near up to the minute protection in the event of a disaster. It also means that when you restore the data, you’ve lost only 15 minutes worth of emails, transactions etc..not a whole day as with traditional tape backups.
Disk Based Backups also allow you to restore data in a few minutes, rather than hours with tape. Another benefit is that users can restore their own files (if allowed) without hassling IT 🙂
That being said, I’d still backup up to tape as well, giving you the added security of off site backups if you needed them.
You can see the Top 10 Benefits of DPM 2007 here.
Cloudy with a chance of Licensing 
Exactly: Disk-based backups are a sure-fire way to not only have a hot backup ready to roll out in the event of a catastrophic situation, but when you have that combined with tape backup or even off-site cold backups, you’ll not only be protecting yourself from critical mistakes, but maintaining job-retention as well.