Oooh, I like this a lot.
That is a little snippet from a query of work items in VS2010 (cropped from a larger pic obviously). You can add a work item and then add other work items that are part of it, break it down into smaller pieces just as though you are in project. This is a huge deal for me! I found this as part of an incredibly long and comprehensive post (with a dozen screenshots) on Brian Harry's blog. This is going to be a must-upgrade for me just for the VSTS stuff - and I love the new editor, and plenty more besides. So far not a single project I've upgraded has had any issues, they've all just worked.