Ryan, I don\'t like to go above ISO 800, but I can basically tolerate up to ISO 1250. On my 5DII the corresponding numbers are ISO 1600 and ISO 3200.
Boris, there seems to be a lot of camera shake blur in the Hut shots, but generally speaking - yes, the corners/edges are relatively soft wide open. You can compare these two examples (open in separate tabs and flip between them):
