OK, I broke down and sprung for the Lowrance Airmap 2000c instead of the
1000. Wow.

Normally I rent a plane that has a panel-mounted IFR certified Garmin 430,
but that may change due to circumstances beyond my control in a few
months.

Obviously I can't file /G IFR without a proper IFR GPS, but this one will
be
used as a backup and for cross-reference at the very least.

So...do I tell a briefer to note that I have a VFR GPS and will the
controllers take note, sending me direct, off airways? Will it make any
difference to them at all? Given the fact that nearly everyone has one
nowadays, will they assume I have a GPS even if I don't indicate it?

I fly with a Garmin 296 on the yoke, the airplane is equipped /A
(transponder and DME), and I always put "VFR GPS" in the remarks section on
the advice of an air traffic controller friend. Since then, I routinely get
cleared direct to fixes way down the road and outside normal VOR navaid
coverage, so I can only assume they are seeing and using the remarks. Many
times, they clear me without me even asking, like to the initial
intersection of a STAR at my destination airport.