1.5.0 (original Linux firmware):
  Combined firmware (includes support for some radio types).
  Nothing known so far.

1.9.3.e:
  Works relatively ok, but some Tx error 0x20 issues suspected,
  and periodic transfer stalls sometimes (or is it a driver issue?).
  Also, the connection sometimes hangs completely (frequently complained about).

1.9.4.7:
  Nothing known so far.

1.9.8.b (from dwl520+_drivers_307.zip):
  Perfect transfer (PheeNet WL-0022), everything ok so far.
