Would be keen to see what people have to say here. I'd be looking for a cost effective way of backing up sbs platforms (incl 2008 and 2011), although currently I just supply 2-3 portable hard drives that the customer swaps in once a week or once a day, keeping the others off-site to cover them in the case of the unthinkable. My monitoring only tells me when backups have completed/failed, but I can't see if customers are actually swapping the disks (although I know most of them definitely do).
I use Backup Exec for most, SBS2003 built-in backup for a couple, and for non-SBS critical machines, Trend Micro SafeSync which is cost-effective and works well (but doesn't have SQL or Exchange options). Comes with iPad and iPhone integration, and can be installed on various client machines to point to the same data folder, facilitating remote working for them.