Julian,
I didn't do much with a GPS in the US, as I was mainly flying helicopters at low level, so looking out for kites and birds and wires was far more important!
Evo and others,
When I did take my GPS, on my first US solo cross country, I discovered the same thing; not much info, though I think airfields were marked. I hadn't known that either.
I haven't updated mine since I bought it 4 years ago, but I only use it really if I think I'm lost or can't find an airfield, and they haven't moved airfields or towns, and I only use it to back up my map reading. If my map falls out the window, I can either land my helicopter, or get a heading to the nearest airfield from London Info or someone similar.
I think this really comes down to using what's appropriate to the circumstances and being prepared to be flexible. If I was flying in the Sahara, round the world, the Arctic, or anywhere similar, I'd get two GPSs and loads of batteries. Low level in LA, and going to the PFA Rally on Friday, I won't even switch it on as I reckon I need my eyes out of the cockpit as much as possible. Most flights that most of us here do are somewhere between those two extremes and it's a useful but optional backup.