One smallish suggestion; I tend to be a tad type A, so I like to have an archive of various versions of any particular application (with SL DVDs costing less than a quarter, why not). So I tend at time NOT to use the update mechanism built into the application because it rarely has an option to save the distribution.
Might it be considered that the update mechanism have an option to "leave" the dmg behind (assuming this IS the mechanism used)?