interesting what you say guys!
who has suggested you to use a GPS for your flights, and when did you start to use the GPS and why?
in my life I used a portable gps only maybe on 5-10 routes as a backup, but I always use normal VOR airways as primary navigation, the GPS is very helpful for Groundspeed and ETA.I think the GPS is kind of boring specially when you are cruising for hours.
I think you can plan some flight on a PC simulator between airports, to make yourself confortable. put some cross wind and see by yourself, if you can still fly.
I use a car GPS, and I love it!