So, one thing I noticed during the stream is that they talk about multiple "fueling" trips per crewed vehicle, but you would think that an unmanned fuel transporter would be able to fully fuel a manned vehicle of the same basic design in one trip. That, coupled with the fact that I find it hard to believe that Musk has forgotten to account for the water requirements of an Earth-Mars trip make me think that maybe there are some pretty significant engineering details that have been considered, but where glossed over for the sake of keeping the talk accessible.
Why bother with refueling? Why not just dock a propulsion module? You save the weight of the return features, and you can leave it in martian orbit and use it to refuel there for a return. But yea, interesting plan. I need to go play Kerbal some more.