Depending on how much data you have, they really start to throttle it on their basic service. I have over 300gb of pictures.
I believe your first 35gb your upload speeds will go crazy. Once you upload more than 35gb they throttle you down to 512kb up, and then after you go over 200gb they throttle you down to 100kb up. If you are shooting raw files it will take forever. Right now I have the basic $55/annual service and i'll tell you the upload speeds are painful, painful to the point where i'm ready to pack up and pull the plug and i've already uploaded 200gb.
Also, if you buy a new computer and want to change file locations give it up. Their migration process is basically you run this wizard and it will re-download all your files from carbonites service. While the download speeds fly, they put the files where they want to put them. I recently upgraded from XP to Windows 7 and I wanted to organize my pictures a little differently (more efficiently using window 7's libraries) and their migration process doesnt allow this, even working with their support it is a nightmare and basically to do it my way I need to re-upload data that is already on their servers. They put the files where they want to put them. I emailed their ceo to complain about upload speed and migration (contact info is on carbonites webpage under contact us) and said your upload speed sucks and they told me maybe I should use their Carbonite Pro
service which is much more expensive than the free service. Carbonite pro there is no cap on upload however you pay per month per gig. Screw That!
I just built a new PC with 1.5tb drives in a raid 1 (mirror) configuration. While it's not offsite like carbonite is, i'm redundant and not wasting my time, bandwidth and it's way cheaper. My 320gb would cost $250/month with carbonite pro.
IMO carbonite standard service is geared towards the common user with under 50gb of data.