GPS systems?

[vegas08]

Someone gave me a Garmin nuvi 760 GPS system as a gift. I've done no research on GPS systems, so I'm wondering whether anyone can offer feedback on whether this is a good system or whether I should exchange it in for another. (The gifter volunteered that I should exchange it if I didn't like it.) If you know of a better model, please let me know.

On a related note, I'd been thinking about getting an iPhone because I'm often in new cities, looking for businesses and such, so it'd be great to look up stuff on the Internet. Does anyone know whether the iPhone GPS is reasonably good enough that it's unnecessary to have a GPS, or would a GPS still come in handy even with an iPhone?

Thanks for shedding any light.