Hi,
I know this is somewhat of a nitpicky request, but I think it would serve the OS X users better.
Is it possible for you guys to host the DMG files up on the server raw? (i.e. not in a zip file)
You can actually make the DMG a compressed DMG with hdiutil, or if you're doing it manually, via Disk Utility, so there's no need to zip it. The compression on the dmg might even be better than zip, not sure about that.
This has the added benefit that users who have "automatically open safe files" set in Safari (or other browsers) will have the disk image automatically mounted.
It also has the added benefit that it won't annoy users who have "automatically open safe files" disabled, because they won't have to open the zip and then open the DMG.