The issue with GPS approaches is to also make sure you have an IFR approved GPS. If you don't have RAIM, then it's like doing an ADF approach without monitoring the audio (what do you mean, you don't monitor the audio?).
Non-IFR approved GPS can wander off and not tell you. There is a whole different method (nearly said approach) to doing GPS instrument flying, and unless you know the whole thing, you are standing yourself and passengers into danger.
And a moving map GPS is far and away the best system to have.
Shawn