I'm very happy with my GPS III Pilot which I've had for several years. It can make you lazy, but I find it invaluable in the following circumstances:
1) Your route is taking you very close to controlled airspace that you'd rather not infringe.
2) You'd planned to fly overhead an airfield; the cloudbase won't let you, and they tell you to route around; you think you can judge 2 miles fairly accurately, but you'd like to be certain.
3) The weather's deteriorated unexpectedly; it's safe to fly, but nav is difficult and you'd rather not get too overloaded when you may need your wits about you should things get worse.
4) You're overloaded in some other way, eg you just scared yourself by getting too near another aircraft or something similar; why compound things by getting lost too; switch on the GPS and make things easy for yourself while you calm down.
Otherwise, I just carry it in case I need it. I don't know how to do anything other than follow the moving map; I did once, but I forgot through lack of practice. But I like visual navigation, and my way saves loads on batteries.
