I've been playing with the web interface for browsing the shares and a few things stick out at me:
1. If you have a multi-page list of folders (music folders, for example) and then you enter one of them, there is no easy way to go back. You can either use the back button (and have to click ok to reposting the form data) or use built in control to navigate to a higher folder level, which will return you to the first page of the multi-page list. It would just be nice if there was a built in control to get around that.
2. When you're downloading something from the server, the control connection that you were using to browse becomes essentially unusable. Until the download completes, you're stuck. It would be REALLY nice if WHS had a built in behind-the-scenes bandwidth throttling ability so that it would make sure the control connection worked and slow down the transfer if need be to accomplish that. If you wanted full speed, you just don't browse around, but it should be seamless to people who still want to browse.