For the feature set you get on the Instinct, $129 is a ridiculously good price. It's worth that for Sprint Navigation integrated with Live Search alone. (With Live Search, you just hold down a button and speak any business or search category, eg. "pizza" or "Dip-n-dots", and it finds hits near your curent GPS location. You can look at reviews, maps, turn-by-turn directions, share the location with another device, or the best part: launch a Sprint Nav session from within the Live Search app to begin realtime GPS navigation.)
Plus, don't let any Apple cultists like SPC try to tell you that the 3G iPhone will be as fast as the Instinct; it won't. 3G on a GSM phone isn't as quick as 3G on a CDMA device.