I have an old PC converted to a local hard drive farm.
I back up everything locally to that machine. This gives me 2 copies locally (the original plus the backup).
I use Crashplan as a third off-site backup. Since it is there in case BOTH of my local copies are not usable, I can tolerate the speed issue (although restore is MUCH faster than backup). Also, I don't have a business that depends on having instant access to the backed up files, so I can wait if I have to.
I don't use Carbonite because:
1. It won't backup attached hard drives (well, it will do 1 and only 1 attached drive, but you pay more money).
2. They do not have a reasonably priced multiple computer package.
3. The do not keep versions of files, only the latest copy.
3. (And the final deal-breaker) They will not keep your backup longer than 30 days. If your computer does not connect at least every 30 days, your entire backup is subject to being deleted from their servers. If you delete a file accidentally, you have 30 days to discover this or your backup copy will be gone. If you pay for the attached drive option, when that drive is not present or powered down, they treat this the same as a deleted file.
All of the above was correct as of the last time I seriously examined Carbonite's product offering. I don't know if it is all still correct, but I don't care since I moved to Crashplan (which has NONE of those issues).
I currently have about 1.5 TB backed up to Crashplan and locally.