heatseeker n.
[IBM] A customer who can be relied upon to buy, without fail,
the latest version of an existing product (not quite the same as
a member of the lunatic
fringe). A 1993 example of a heatseeker was someone who,
owning a 286 PC and Windows 3.0, went out and bought Windows 3.1
(which offers no worthwhile benefits unless you have a 386). If
all customers were heatseekers, vast amounts of money could be
made by just fixing some of the bugs in each release (n) and
selling it to them as release (n+1). Microsoft in fact seems to
have mastered this technique.