I signed up a while back and have to say that I was glad to see this latest Mac update as the upgrades/changes are much improved over the previous version.
Like all beta software I've tried, there are some things that could be done better and hopefully they will take the comments I sent them into consideration... At least the responded with some questions so I know they are considering it.
Being able to set up private networks with my friends keeps my personal stuff from prying eyes, I don't see why everyone wouldn't use this type of service over public posting/uploading to websites.