i've been using the Google Maps Navigation (beta) that just released a week or so ago and actually can't fault it, plus it was free
turn by turn nav, and it actually increased the accuracy of the previous version, plus on my MyTouch, the recalculation speed is far better than my garmin nuvi 680 - on last test trip across town, i took 3 shortcuts off the route it had picked using the major thoroughfares, and within 3-5 carlenghts of making the turn off the calculated route, it had rerouted and was even announcing the "new" next turn
give it a try - won't cost anything - ony reason i'll be downloading CoPilot when my new micro sd comes in, is the google maps are "iffy" if you go into territory (like WVA) where there's no cell svc and turn your phone off - no way to download maps again until you're in cell svc area