Sean,
The S15 is meant to be used as a rear projector and the G15 is a front projector.
There is a real difference. The S15 has a fixed short throw lens, and requires that you align the
center of the lens with the center of the screen. This would put the S15 right in the middle of your
line of sight if you used it for front projection.
The G15 has a longer throw 2.1 to 3.1 zoomable lens with 50% offset - that is you align the lens
with either the top or bottom edge of the screen depending on whether you have a ceiling mount or a
table mount configuration.
Another poster wanted to use an S15 for a front projector and Tom Stites of JVC pointed out that
it was not a good idea. See:
http://www.avsforum.com/avs-vb/showt...threadid=91437
Greg