IFR with a VFR GPS

You don't have to play any games with "radar vectors" nor do you have to put
anything in remarks. If you want to go direct then just file direct.
It
doesn't matter what you're using for navigation, just be able to fly
what
you file.

I don't bother trying to file "direct" as here in the northeast I'd
never get it. Besides, I never file above 7000ft and I end up with a
canned TEC routing anyway. I've been asked on several occasions by ATC
if I'm able direct to (fill in the blank) and the Garmin 150XL can take
me right to the intersection/fix.