I use spideroak as well, mainly because of it's flexibility (partner uses same account, only syncs the necessary folders) and the fact that it's cheap (at the time I signed up; especially considering many people can use the same account)

But man, is it slow! (OK, I realise it's encrypting locally, but even accounting for that it just "feels" clunky compared to the competition)

Also, I can't seem to view pictures using the online account file browser. It seems to suggest that thumbnails will be visible before downloading, but it never seems to work :(

Otherwise, it's really good! (I also have a skydrive, GDrive & a dropbox account that I use for quick sharing, save game backups, etc -- They've all got their strengths)