Pocketpcthoughts just published a review of Socket's CF Bluetooth card.
"...the Bluetooth connection kit from Socket includes a CD ROM, manual and PCMIA sled to go along with the card itself. Speaking of the main hardware, it's as small a card as you can expect in Compact Flash format, the same size as Compact Flash memory and because it's compatible with Type I, will be usable in any device with a Compact Flash slot. Due to the small nature of this card, there have been misleading reports that the antenna is actually internal and that this will impact on performance. On the contrary, the antenna runs along the top of the card which will be the outer most edge when installed in your Pocket PC meaning it has a good window to your Bluetooth partners. It also means there are no protruding parts to this card making it ideal to leave installed when using a case for example."