Been using Dropbox for all my files (I keep it under 100GB) for several years now. So far never had any problems, in fact they saved me from lots of tears when they recovered an accidentally deleted folder beyond the 30 day limit for me. The collaboration and sharing options are another huge plus. I frequently give out the link to a folder which results in a beautiful and intuitive website view of its contents for the recipient. I also have a shared folder with every member of my family which is much more convenient than sending file attachments around. These last two sentences are also why I wouldn't want to jump ship to Amazon despite the attractive price: At least in my case Dropbox has realized a network effect that more or less locks me in.

I did quite a bit of research into other options before and while using Dropbox: Tried GDrive and found the online interface (GDocs) not suitable for the amount of content I have, tried SkyDrive when it was still Live Mesh and had tons of problems with it (hour-long delays when syncing). At one point I tried a peer-to-peer type system (I remember their logo being red, forgot the name) and it was Java based which made it annoying to me. And I tried a system where files were encrypted before transfer (some Dutch company, again forgot the name) and the problem with that was that it was way too slow at dealing with all my files.