Whilst I was teaching I generally didn't even mention the GPS until after the first solo nav. I introduced it at a basic level after that, but as a general rule it would be off most of the flight.
I told most of my students its a useful tool, once they had their license we could look at them more in depth. I wanted them to rely on heading and time as you won't always be in an aircraft that has a GPS and letting them use it too early tends to develop a reliance on these sort of things.
Just my opinion though.