A good description of the process but DON'T do this if you want to keep the functionality of a BT mouse (especially M$) or BT keyboard. A number of people (me included) are reporting on Apple's discussion boards and MacNN that the Apple BT 1.5 update disables some mice and keyboards (including Apple's own hardware).
I suspect a bug in the D-link firmware updater but can't prove it yet.
The BT 1.5 update works fine with the M$ BT adapter and M$ BT mouse but then there is no headset functionality. When using the D-link adapter (1.02 firmware flashed) I have also discovered that if you connect another audio device such as a wired USB headset while the BT headset (Jabra for example) is selected in Sound I/O, after the new audio USB device is disconnected, the BT headset loses all audio output until the Mac is rebooted.
In short, on my setup, this BT1.5 upgrade still needs a lot of polishing!