Yes - without the 3G you will get no location based app nor mapping and navigation apps
Actually, no, without the 3G you'll also support location aware apps, only through WiFi geolocation. Apple uses the infrastructure from Skyhook Wireless, which is also used on the iPod touch. Precision is not as good, though.
That was the only thing I was confused about. So the wifi only ones have no GPS... thats a real bummer.