I've been using SpiderOak for about 6 months and really like the service. It's much more sophisticated than Dropbox, and your data is encrypted before it leaves your computer. You hold the encryption keys, not them. They recently introduced a feature called "SpiderOak Hive" for those people who would simply like to organize all their synchronized files under one main directory, like Dropbox does. Otherwise, you can individually select which files and directories get backed up and which directories get synced with which other directories on other machines. This is really useful if you do cross-platform development and wish to keep configuration files synced between machines.
There is only one area where I think Dropbox is better, and that is speed of sync. Sometimes I work on a piece of code right up until I shut down my computer at the office at the end of the day. Dropbox usually has the file synced within seconds, while SpiderOak may take a minute or more. For this scenario, I either use a flash drive or the free level of Dropbox service.
and the mobile apps are shit from spideroak. you actually can't upload from mobile which blows.
