Personally, I can't stand double clicking a disk image file (.dmg) on the Desktop and not getting instant notification that the disk is being mounted. This is probably not as much of a problem on newer, faster Macs. However, depending on how many processes I have running at the time, it can take my iBook G4 a while before it displays the disk mounting progress dialog.
As a result, I often end up double-clicking a disk image more than once, thinking I may not have properly double-clicked it the first time. Often times, I've just resorted to highlighting the file and using Command+O to insure that the disk will mount soon.
Here's one way to make the DiskImageMounter application icon appear in the Dock while mounting a disk image. This will provide you with almost instantaneous notification that the disk mounting process has been successfully initiated, even if the dialog box is missing in action.
$ cd /System/Library/CoreServices/DiskImageMounter.app/Contents
$ sudo cp Info.plist Info.BU.plistProvide your admin password at the Password: prompt.Mac OS X Hints
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