I was happy enough to have the push email and calendar. Now I find out there's something new that I have to investigate
Where is that?
In Preferences, select MobileMe, click on "Back to My Mac" and click on Start. Do this on at least two computers that are logged in to MobileMe using the same account.
Secondly, make sure you have started the services you want. In Preferences, go to Sharing and enable what you want. I suggest File Sharing and Screen Sharing. Do this on the computer you want to reach from the outside.
Now, in Finder, if you click on SHARED in the sidebar, your other computer should show up in the list. Click on it, and you'll see the disks of the remote computer. Click on Share Screen to get connected to the screen of the remote computer. The good thing is that this works across the Internet. When I'm at work and click on SHARED, I see all my colleagues' computers, and I also see my computer at home. Everything works the same way it does when I'm at home on my local network.
If you're using a gateway at home it has to support UPnP. If it doesn't you might have to open up some ports in the gateway.
Anyway, Back to My Mac is a really nice feature. It just works. In the background, the two Macs are opening en encrypted VPN tunnel to communicate securely.