The thing I like most about it is that it's totally transparent, moreso than the Dropbox client. It also does some kind of transparent archiving (easily switched off on a per-file or directory level) that removes local files if they haven't been used for a while and automatically re-downloads them if you try to access them. Perfect for directories full of photos.
The biggest flaw I've found is that it doesn't support long path names. npm stores its modules in very deep directory structure that absolutely will not sync.
I trust that Microsoft will be around longer vs. Dropbox in its current form, but I'm still not convinced that Microsoft 'gets it' yet. With the new third-party cloud integration in iOS 8 and Yosemite I think this is a great opportunity for both to pick up a lot of users, though, and it'll even the playing field as far as engineering goes, so this is a good time to be on either one.
What they should do is partner with Corel and offer Wordperfect X7 with Pro, or have a $129/year version that includes it.