Does Visual Studio Team System support attomic commits/check-ins?

Yes. Multiple files checked-in at the same time are atomically committed to a SQL Server 2005 database and a referencable artifact known as a ChangeSet is published. This can be used at a later point in time to view the contents of a check-in, associate to work item or build. It can also be used the same way a label would be used “Get me all the source code as of ChangeSet 155” which would include the image of the entire source branch (not just the changed files) as of that moment.