Assuming a non-virtualized environment it a good idea to take actual images of servers (using something like Acronis True Image) and store them on\off site?

Backing up data is great but I feel it would be good to have copies of OS images in the event hardware dies or an upgrade gets botched I can always revert back.

What would be your recommended way to do this (preferably using a NAS and an online backup service)?

I was talking with the Iron Mountain folks and the service they described is more geared toward taking incremental snapshots of data. I'm not sure if there's a way to backup images in an incremental way such that only the changes between them are saved (that way I'm not wasting X GB each time I take an image).