The Best Cross Platform Folder Share Service?

There are so many "hard drive in the sky" services these days that I honestly can’t bring myself to wade through all of them and find one I like.

Here’s my application. I’ve now moved back to Windows in the office (xobni/outlook being the driver) and still using MacBook Pro for home/on the road.

I want a folder share service to share one folder (my documents of course) between both machines and also into the cloud.

I’ll take any and all the advice I can get but I’d love to hear from people who are doing exactly this.