I actually used Google health along with members of my family.
Main use is each member has any list of medications and and importantly "Allergies".
I used to have a piece of paper in my wallet with this information, this was much more convenient to access from anywhere I needed. It was good for an emergency, any when in a medical office visit where you have to fill out some form, and honestly I can't remember all this crap at this age anymore.
It really is handy. More convient then scratching things off a piece of paper and updating it. Now I don't know how many people are in the medical industry, but there are lots of sites that are HIPAA Compliant that you can pay for, for this type of service, but Google was free and I could care less if the world knows about my Google logins allergies. The trade off was fine.
This however is just another straw in the "Cloud" coffin.
I think something like Opera Unite is much more interesting (The implementation is far from perfect), but an easy users side "Server" with plug-in blocks that can have 100s of mini servers serving anything--- WhiteBoard server, Web server, Music server, Video Server, Medical server, PostIt Note server, etc....
No, Opera Unite, does not go through Opera.com. It can use a DynDns style url for easy access through opera.com, but you can access it directly through your IP and port #. Again, just the concept I think is more interesting anyway then the cloud. Any easy server, with "plug any anything" server modules.