Is the portable RAIM capable? Currency and thoroughness of the database? That might be one reason for the legal stuff.

I'd not use the GPS during your IFR training. It's too easy to become reliant on it. You need to know how to use the certified tools in the plane without using the GPS as a verifier, although it does make life much, much easier.

On another message board, it has been brought up that you can use a VFR gps for IFR flight under the guise of Radar Vectors from ATC. I'm not sure if I agree on that one.

Congrats on the PPL and good luck on the IFR!