I had some places to get to today and had the opportunity to try out the newest beta 1.2 of xGPS for turn by turn directions with voice navigation while driving to my destinations. It was a pleasure to use and I got where I was going on time without issue. If you haven't jailbroken yet this is yet another reason why you need to. TomTom and TeleNav haven't been able to get the turn by turn voice nav out the door (presumably because of Apple's restrictions) but for jailbreakers a public version of xGPS with both turn by turn and voice nav will be out via the MMi Cydia repo later this month -- maybe even as soon as February 20th!