heatseeker

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 is someone who, owning a 286 PC and Windows
   3.0, goes out and buys 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 the
   bugs in each release (n) and selling it to them as release (n+1).