I favor Box. Great cross platform support for me so far... Windows, Windows Phone, webOS, Android. I've used it on all those.
I know they also support iOS and Blackberry. There is a Box sync for Mac as well.
I have Box integrated into my Office 2010 and can save any documents straight to the cloud.
Online, Box offers truly flexible share and permission options inside the folders you create and on a file by file basis. IMHO it offers far more than Dropbox which I tried once (just for name recognition) for an internet project I had put together... I ended up moving it over to Box so I could make the file permissions and downloads happen how I needed them to.
Also, Box has device bounties to increase storage. They are not cumulative, but it easy enough. Just log in from a selected device and get bumped to 50GB for life. I earned mine from logging in with a TouchPad way back in the day. I also saw it for Nexus 4 and that is how I know it isn't cumulative. Chances are you have a device or can borrow one that will get you bumped up, you just have to find the right one and log in from it.
https://www.box.com/about-us/