Thanks Steve. I'll do image backups for the system disks and file backups for the data.
Typical system disk is 75GB and data will range from 40GB to 250GB/system. My effective upload speed is about 280 mbps.
The version vs retention question is a tough one. Retention period is OK for most things, but for that infrequently-used access database, by the time someone realizes that the current version is corrupted, the prior version might be several months old. That said, most files probably only have one version ever. And I also have one system that will update 80 mb of files every day (same files), so keeping 30 or 90 days can create some size, though I guess in the scheme of things it wouldn't be a big deal. I'm very interested in what you see as the tradeoffs between the two approaches. I do know I've found using the S3 versioning to be pretty non-transparent and backup buckets seem to creep up in size forever.