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.

Bitcasa actually is pretty good, surprisingly, if you have lots of small files or good bandwidth. The clients are pretty buggy still though. I can stream mp3s from my home cable connection but videos and images are -pretty- delayed. It'd be impossible to use for something like storing a photo library. But it's a good place to dump all the legal media you've been torrenting over the years.

Dropbox is still the best in terms of experience and support in other apps. Price is quickly becoming not competitive.

Google Drive was crashing with folders with largish numbers of files in it (on OSX) so I couldn't test much after signing up and dropped it. It seemed fine, but Dropbox has more integration points.

Amazon Cloud was pretty useless until this announcement. But their cloud player is pretty awesome and if you sign up for their cloud drive, you get the cloud player premium.

Really, if Dropbox doesn't get something moving price-wise, this could be the end. But man, I love me some dropbox. It's just $$$$.

I used Bitcasa for a bit, back in the free version. The UI left a bit to be desired, and their encryption is lacking. (See http://blog.bitcasa.com/2013/03/18/we-dont-show-and-tell-inf...).

Right now it's not 100% cloud-ified, but my current favorite is AeroFS for syncing between machines. It works quite well. Here, the security risk is that someone gains access to your account and syncs all of your files to their system. I'm planning to work around the lack of a web client by installing a WebDAV server for myself, when I finally get around to it.

Switched from Dropbox to Google Drive a few months ago. the UIs are very similar, and Drive is much cheaper. My only complaint has been syncing:

1) After a week of repeated attempts, I gave up trying to get video from Dropbox to Drive. Maybe the files were too large?

2) Also, syncs are faster and more seamless across devices with Dropbox. There are noticeable lags for most syncs with Drive, even small, single files.

3) Event when Drive thinks it has synced, it hasn't and I have to restart the app.

There are other benefits to Drive, but I never had any sync issues with Dropbox.