Actually it is pretty rare that I get the thing out of it's bag, unless I'm going somewhere I don't know that well and even then it really is supplementary, but a fantastic back up.
No nav aid is perfect, though GPS is very, very good. It won't stop you from flying into a mountain, just give you the information that should make it impossible for you to be that stupid!
Personally I think that GPS makes navigation incredibly easy and far safer, but I think the point that Pat Lander was making in the Trainingcom is that GPS units can be relatively complex if you have never used one before. Most people only know how to use the absolute basics and don't know the capabilities of these systems.
If you have an out of date database, then you have no warning of airspace changes etc. (as mentioned by Pprune Radar earlier), I think this is one of the things people need to learn about GPS before they become reliant on it. Often people are unaware of the limitations, especially things such as aerial mountings and what happens when you get near sites that put out alot of radio interference.
If you understand the limitations of any system, then you are a much safer pilot than one who blindly believes that the magic box will always keep you out of trouble.
As an aside, we are about to order a Diamond DA-40 and have been warned off the Garmin 1000 kit by the manufacturers, since the a/c will be used for hire. They are worried because people need a 2 day course in how to use the avionics because they are so different to the norm and that people will get into a lot of trouble. It may be a bit of an over-reaction, but I have to respect their view point.
I actually agree with them, even if I am a bit dissappointed myself since I would love to have the glass cockpit version. In fact what we will probably do is that when we get a second one we may have that with all the toys, once our members have got used to using something that is a bit more familiar.