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>>>Update<<< Chameleon 2.0 for Lion here:
Here you can read how to fix your CSR bluetooth dongle: prasys article on bluetooth
There are many Bluetooth adapters out there, all of them more or less compatible with windows. If you want to use Bluetooth on Mac you have to find out which Radio and Firmware it uses. Some of $2 dongles will work under mac. If your Bluetooth adapter isn't compatible out of the box, then you might be able to flash it to compatible Firmware. Flashing firmware requires bluetooth dongle which can be flashed. Usually those bigger ones like D-Link DBT-120.
The best compatibility you will get with D-Link DBT-120 v1,2,3, and b4. You will be able to flash it with Apple own bluetooth Firmware and thus get the max compatibility. Flashing can be done only on Tiger as the software doesn't work on Intel Macs. So if you have G5 or even G4 with Tiger or something older (it works from 10.3) I advise you to buy it, and you will never have problems with bluetooth. This dongle also works in BIOS (HCI HID automatic switching only when USB legacy is enabled in BIOS) so after it's plugged in you can trash your wired one.
Mac Compatible Radios:
CSR - Cambridge Silicon Radio (Vendor ID 0x0012)
HAMA Bluetooth Nano - 5276 also 52.76 couldn't be Flashed (works on real Mac)
OEM No Name - 1963 also 19.62 couldn't be Flashed (works on real Mac)
Broadcom - Vendor ID 0xa5c
Only those versions are supported by Apple: Broadcom BCM2045/2046
Needs custom .kext or kext patching.
Compatilbe Bluetooth Dongles: (please do your own research, sleep might not work OOB)
Asus USB-BT21 Mini Bluetooth Dongle Asus
Bluetooth 2.1 USB Adapter (15542) Trust
Belkin Mini Bluetooth-Adapter Belkin
Trust (Broadcom BCM2045A)