I've found the bluetooth devices that come with a dongle
which emulates a USB device to be much more useful than
the ones with a dongle that is "native" bluetooth.
You don't need any bluetooth software on linux to be
working at all, so there is much less source for troubles :-).
If it is a keyboard, you can actually use it in the BIOS.
On the other hand, that means the dongle isn't generally
useful for bluetooth connections, but is pretty much
dedicated to the one device.