heatseeker
heatseeker: [IBM] n. 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).