I would be suspect, too.  They telemarket HEAVY; "window replacements,
vinyl siding, etc."  Very heavyhanded and rude!  They lied to me when
they claimed that they were local manufactors.  (It's a good idea to
purchase from local businesses for a number of reasons)

BTW:  One reason to purchase locally is the possibility to convert
single-pane to dual-pane without frame modifications.  Locally,
Redding CA, the major supplier of windows to local contractors is
Western Glass (and has been for years).  Their alum dual-pane panels
swap exactly with the earlier single pane sections.  I have found a
number of dual-pane panels at the dump(!) and at garage sales, etc.
This is certainly a "frugal" method to upgrade your windows!  Even if
one had to purchase the new, dual-pane panels, there would be a big
savings over cutting out and replacing the entire frames!  (Of course,
if you have older construction, "double hung", this option is not
viable.)  But, AVOID "Pacesetter", IMHO.