Day two has been pretty uneventful. MSE has not detected any threats (Neither did Avira, as I avoid the nastier parts of the internet), and has been VERY unobtrusive. I have yet to have any virus definition updates, but will try an update tonight. I would imagine the definition update would be rather small in comparison to the initial database download, but I could be wrong.
Otherwise, there is really nothing special to report, which is exactly how things should be with an antivirus solution: I should not see anything of it unless 1: there is an actual threat on my system or 2: I choose to have interaction with it. Otherwise, I should be able to pretty much forget it is even there.