Microsoft has updated SharePoint Online with a patch that resolves the bug that prohibited you from getting the service descriptions from the web services, that I previously described.
This means that you now can use Visual Studio or SharePoint Designer (or any other tool that you like) to connect to the SharePoint Online web services and code away, instead of going to some local instance to get the descriptions.
Does anybody know where the Microsoft Online team posts all updates/changes to the BPOS? I got this information from Troy (from the BPOS team) commenting on my post.