Not a significant portion, no. CrashPlan is only my third layer of backup, the offsite backup. Each of my drives have a clone backup drive (typically just a WD My Passport that makes them easy to transport when I travel), and then a larger external that holds backups of all of them--I usually keep that one in storage and only plug it in once a month or so to sync. CP is the third layer of backup. The most I do in a typical week is use the Android app to grab a few movies or documents from the CP storage to get it onto my phone and tablet.

I should probably "test" doing a recovery from CrashPlan at some point, but I fear that even getting a third of it (1TB) would probably trip some sort of overcharge from my ISP.

I have. It was decent. accidentally hosed a vmware image and it was easier for me to just pull the whole thing down from Crashplan. Speeds were decent, limited mostly by my cable modem. I don't recall the exact throughput but I remember looking and saying "Hey, this isn't bad" and not being annoyed by anything.

Plus the price isn't too bad.