Our current backup scheme is to backup all of our servers to a NAS device, and swap it out with another one occasionally. Of course, this is no fun to manage, so we've been evaluating Microsoft's DPM.
So far, DPM looks like it will work great, but the only thing I haven't been able to figure out is how we can copy the backup data from DPM to a NAS or other external device other than tape to be moved offsite.
We are looking at Iron Mountain's CloudRecovery solution, but wanted to also look at a sneakernet solution, if possible.
I wrote a Microsoft DPM 2007 review a while back, and the stuff in there still holds true. If you're going to get the DPM data off the DPM server, you have to use a separate backup product that can read DPM's volume structure.
I'd recommend going through the entire review (not just because I wrote it) because there's a few other gotchas. For example, your problems with a NAS device will recur on DPM - there's no "pool" concept in DPM, so if your one DPM server goes offline, your backups fail and you can't do restores. You'd better be really sure your DPM server is reliable.
I found it is possible to backup a DPM server with a secondary DPM server. Our solution may be to have a second DPM server at an offsite location.
http://technet.microsoft.com/en-us/library/bb795680.aspx