If you use cloud storage not just for your files, but also for music, movies, and other content, Streem is a new service that specialises in both. The platform offers unlimited storage for all of your files and media for $US20/month, complete with cross-platform desktop and mobile apps.
One of the nice things about Streem is that you don't have to sync your files with every device -- you can upload whatever you want, but you don't have to keep a copy on all of your computers in order to access them. As long as you have an internet connection, you're set. File are streamed to you when you request them, and use adaptive bitrate streaming so you get the best possible quality for the internet connection that you have available. Streem even transcodes your media on the fly so it plays back on whatever device you're using.
The service has native apps for Windows, Mac, and Linux, as well as mobile apps for iOS and Android. There's a webapp too if you don't want to install anything, and the developers told me that support for Chromecast other TV-connected devices is on the way soon.
That said, Streem does involve some compromises. There's no free plan to find out if you like the service before signing up, and you have to hand over a lot of rights to your content when you upload (rights you do get back if you remove your files.) Te Streem team says that those rights are required in order to let you share and stream your media freely.
Also, while your files are encrypted, Streem has the master key, and can decrypt files if necessary. They explained to me that they have employee logging and a "dual key" system in place so no files can be decrypted without two authorised employees "turning the keys simultaneously" as it were. You could also encrypt your own data before uploading it to the cloud, something we suggest you do anyway if the data is sensitive at all.