I'll be honest, Live Mesh: It's not me, it's you.
You're too slow.
I need something larger, faster and more flexible.
I'm in love with Dropbox. (Disclosure: that's a referrer link from my user ID; I get free space if you sign up.)
To be fair, Live Mesh was (and is) a great idea. Unfortunately, it's been in its "Tech Preview" state for far too long. I can live with technical preview status, but what comes with that status is a 5Gb limit, which I just can't survive any more.
I want my data to be on someone's cloud, somewhere. I'm perfectly comfortable that I can encrypt my own stuff as I need to, before handing it over to somebody else. And Dropbox appears to fit the "someone else" bill pretty much perfectly.
It works across platforms; it has a browser interface; it does everything that Mesh does (that I want, anyway), but does it faster and more transparently.
Oh, and it does photo sharing as well. Picasa's going to get a run for its money, here - this is so incredibly easy to store and arrange files on that I'm seriously considering ditching my (paid-for) Picasa web albums.