Good luck with that; I don't know if Minecraft's netcode is terrible or not, but a 1 Mbit up connection could not even support 1 additional player when I hosted a listen server.
As for the game itself, it's pretty fun ... to a certain point. I feel that the real potential of minecraft lies within the multiplayer scene, and so far mini game modes like monster survival or neat things like that have failed to make it into the game. Ultimately, the lack of 'proper' multiplayer support is what caused me to stop playing the game, even though I bought it in alpha. It really has great potential (it's a true sandbox, multiplayer survival), but I don't know if he wants to take it in that direction, although it seems like the natural thing to do given the feel of the game as is.