Not a problem with TFS but with the client. It just doesn't like being disconnected. If, for example, you're working on the train, forget adding new files, the TFS client when it can't talk to the server has massive problems doing that, and I've ended up having to copy new files out of the source tree, delete them whilst the client is active and talking to the server, then drag/drop them back in so I could finally add them
Had that issue with the 2005 client but have been using TFC-2008 with TFS2005 and it seems that the only thing it can't do offline now is handle renames. Adds/Edit/Deletes are fine.
My biggest issue is that if you lose your connection to the TFS server *after* you open the project while conencted things go very wrong! Used to have this while working on the train, connected to the TFS server over 3g, if you make a change while you have no signal, the change is lost. These days I always offline the project first (also a pain as there is no 'Take Offline option'), make the changes and then bring it back online when I have a good connection.