My initial seed took something like 6 months solid (1.5 odd TB and <1Mbps ADSL2+). I just created a backup set with important stuff like photos first and got that up. The initial seed was maybe a month. Then I thought why not and added less important things and once they're there, it's done.

Note that if you pay I would recommend you use the Cloud feature for a last resort backup. Just keep your utmost important stuff if you don't want it hogging you upstream. My "master" backup is the cloud but I also just set up a local copy on my MythTV frontend machine so it's easy to get large volumes of data back quickly. The cloud then basically becomes the "house burns down"/"lightning strike"/"natural disaster" backup.

Also, you *can* provide your own encryption key so that Crashplan themselves cannot even decrypt it. The web restore doesn't work then either as a side effect. You just need to keep that key safe as you have the only copy of it.