Although lat/long is technically acceptable, my experience is ATC
doesn't like them and dont know where they are. Also, they don't know
how to call them out. ATC prefers VOR/DME, which you can use the GPS to
find if you know how. But the best thing IS VOR's or airports. Although
intersections SHOULD be ok, I've seen ATC not know where some are. The
VFR waypoints are excluded, I guess they didn't want to go there. Best
thing these days seems to be to file direct and take what you get
UNLESS you fly it all the time and KNOW what ATC is going to give you,
in which case, file THAT.

It's a bit of a quagmire and I've filed one route, gotten my ground
clearance for a second route and then once in the air, been told to
fly a third. Which is why I just file direct (which is the fastest
anyway).