I didn't originally order the bluetooth option, however I purchased it
from Dell after I had the laptop. The original price was about an
extra AUD$90.00, however purchased separately, they charged about
AUD$20.00!
I preferred this option to buying a USB bluetooth stick, because the
dell bluetooth add-on fits inside the laptop (under the battery) and
lights up the bluetooth LED when enabled. It was surprisingly
small - about 3cm x 1.5cm or so. The plug hidden under the
battery must be just another USB port, as the bluetooth device shows up
as a USB device when plugged in.
I tested the bluetooth functionality with a friends bluetooth keyboard,
from his Dell Axiom PDA. It worked well throughout the office
well beyond 10m (even through a few thin walls).