I have bought the BTD 500 USB Adapter together with a MM 500-X headset. I already have a USB Bluetooth adapter, but this has not apt-X audio codec, which like loud Sennheiser audio quality to have as a cable. And contrary to the adage "those who know radio takes Cable" Is that absolutely, the sound quality is indistinguishable from the supplied cable. Compared to the standard Bluetooth audio codec that's an improvement. The size of the adapter is roughly equivalent to a USB flash drive, so it should do on a PC no problems on a laptop he is a little too big. Software is not supplied with, the adapter is recognized by Windows (Win7 and XP) automatically as a USB composite device (with audio and HID) and works "out of the box". Under Linux, what is important to me, however, it looks different. Just about the BTD 500 USB with the standard Windows drivers working under Linux (openSUSE 12.1 kernel 3.1.10-1.13) has the usbhid driver problems to configure the adapter. The BTD 500 USB crashes here and does a USB disconnect / reconnect and the endless. The audio portion of the adapter works if is communicated to the driver that he should ignore ubshid the Sennheiser Device (For experts: Quirks = 0x1395: 0x002c: 0x4). Here then are the buttons for fast forward, pause, etc. on the headset has no function. A star deduction because a little tinkering in Linux necessary or not completely conform to the standard drivers. The reach of 10m can only be achieved with a clear view. A (thin) Zeigelwand intervening goes (Then it but max 3m.), 2 walls - no chance.
Yet Additional info: The BTD 500 USB is a Bluetooth USB dongle which can for example files transferred to a smartphone. He is only recognized as a sound card.
Addendum: With quirks = 0x1395: 0x002c: 0x8 adapter under Linux works without problems. Now with 5 stars :-)