One thing about most OEM nav systems is that they're hardwired into the car-- so if your GPS signal fades, the car still knows where it's going. I've got a Mitac MIO pda with GPS (iNavigation software bought separately has the best route planning I've found; it's almost always what I would have done). My PDA will often get confused going over overpasses that criss cross over each other. Directions get messed up in this situation and you need to know what road you wanted or else it'll confuse you.

My wife's Lexus nav system has more POIs, I think, than my PDA. She found the "Ross" clothing store in her's. My PDA, on the other hand, displays the planned route better than hers. It's a lot easier to know what street's it's taking you down ahead of time and can avoid certain roads much more easily. Unfortunately, that's not one of the things you'll be able to know until you have worked with the different software programs.

Also, be careful about aftermarket software / map companies. Most, if not all auto makers use Navteq maps. I find these to be quite good in Southern California. I've had bad luck with Teleatlas maps. A MAJOR exit was missing to the airport and that particular program routed me miles away before getting there via the back route. All maps will have errors but it's been said that Teleatlas does better for country roads than city. Again, it'll be something you need to try in your area before you can tell.

Another feature that might be worth considering is traffic updates. I hope Honda strikes a deal with XM NavTraffic, but I don't anticipate it working. Tom Tom's service is cheaper anyway.

Finally, if you're going the aftermarket route (epsecially if you rent cars frequently), I'd recommend a PDA with either built-in GPS like the Mio's or GPS via bluetooth. You can potentially get a lot more functionality out of such a device than a stand-alone GPS unit. Your pick of software is much wider too. If you get a PDA phone, that's one less thing to carry to boot!


-- Frank