[Nickles]

alrighty then.. i've just given both Garmin XT and iGuidance the college try.
iGuidance is the better app (IMO).. the maps are MUCH smoother, and displays all street names, not just the major ones (annoyance with Garmin in the lack of street lables, unless zoomed ALL the way it..)
iGuidance was excellent in the way it gives you PLENTY of time for advanced turns, and will even notify you 2, or 3 times, depending how far ahead your next turn is.
love the TTS announcements.. incredible.
The maps were smooth, same NavTeq map database as garmin.
I did like the lookup functions of Garmin a little better than iGuidance though. iGuidance 'contact' lookup was a little awkward..
iGuidance had a MUCH better POI display.. i was able to click on any POI while in route, and it would display a window of the phone number and detail of that POI..
couldn't seem to do that with Garmin..

all in all, i am sticking with iGuidance, and un-installing Garmin.
reasons : Real street name announcements, very early warning turn notification, smooth interface and excellent map rendering..