NiMH and Alkaline batteries should be just fine for your GPS. Its the lithiums that they're starting to say we shouldn't use due to voltage issues.

Man, that would really bum me out. They can be expensive. What kind of GPS was it?

So far I've never had a GPS unit failure. I've been surprized by dead batteries (thus the criticality of bringing spares), but even my old old Garmin GPS + is still working just fine.

Ken