+1Garmin NUVI series FTW. Although Google Maps on iPhone is also pretty FTW.
+2 I use Nokia E90 and its not too bad. It doestn come close to Nuvi 770 though.I just use my phone, N95 kicks iphone's a$$.
Just make sure the either it has an extrnal antenna thingy or you need a place to put it so it as clear view of the sky.