Want GPS that cant do turn-by-turn directions, and still needs at least a cell tower connection to work? Get the 3G. ...or the iPhone I. Pretty much the same there.
I disagree with you there, bud.
You're right, it doens't have turn-by-turn directions. But there should (hopefully) by one soon. As of now, google map is the only map application on there, and yes you need a cell connection to be able to load the map on the fly. But when the turn-by-turn application comes out, I'm pretty sure that the maps are going to be pre-loaded.
Even with just google map, GPS is so helpful! I was thinking the same thing you did, but now that I got one, it's so much better. I get GPS signal even when I'm indoor. Why is it useful? It knows exactly where you are, so when you are really lost, you know where to start to get back on track. Where the cell triangular method gives you a huge a$$ circle, and you still have to zoom in and try to find where exactly you are. It won't be really useful until you really got lost somewhere.
Oh and 3G is so much better than I expected
It actually feels better than my old iPhone, it's curvy and smooth. It feels like holding a bar of soap
So, to answer the topic, if you are going to unlock and use it on T-Mobile or some other provider that doesn't have 3G or is not supported by the new iPhone, I'd suggest you go with the old one. Since it's a lot cheaper and you wouldn't be able to use 3G anyway. (unless GPS really worth the extra $ to you)
However, if you are going to use it on ATT or other provider that the UMTS frequency is supported by the iPhone, then I'd say wait a little for the price on ebay to come down and then buy it. It makes almost no sense to rush out and grab one on ebay for $$$$$$$$$$too much$$$$$$$$$$$$$$ right now (unless, you need it right now and is worth the extra $$)..