The Sigg 300ml insulated flask is very nice to drink from. As far as actual reusable coffee cups go, the Rivers Wallmug is the best one I've found so far, though it's not designed so much to drink without the lid on.
You take the little tea strainer bit out if you're not using it. I drink from the "lower lid", as it were. Nice rounded shape. You do have to have both on but you could equally take both off at once drink straight from the flask.
The Sigg 300ml insulated flask is very nice to drink from. As far as actual reusable coffee cups go, the Rivers Wallmug is the best one I've found so far, though it's not designed so much to drink without the lid on.