Blackfin1,
As it is an electronic product from the dealer, generally they do not let you return it once it has been hooked up, I think if you go by the dealer and try to test drive the nav system on the lot, you will get a better feel (try the voice, find a POI if any are loaded, etc). I am fine with my nav system since it was part of the Tech package, but I would have been royally pissed if I had paid MSRP from the parts dept for it post sale. If you give it a look on the install instructions
http://lib.store.yahoo.net/lib/yhst-24809172479195/cx5navigation.pdf
You can see if you have the antenna (more than likely) hookup and route that to where your handheld or other self installed unit would go.
As far as the nav, I only need reference once in a while anyway, and TomTomHome lets me load voices or other stuff, but for my needs, it is mostly a dead button anyway, my phone has nokia maps with voice direction if I need it....
I may be equally frustrated with the TomTomHome due to the lack of ability to find established addresses when I use it to plot a route, and the lack of a big multi point route feature (sometimes the trip is the vacation...), so that is as much of a turn off to me as anything else. Go to the TomTomHome site and download it to play around with the maps and route planning as well.
As this is a first year platform, the wait and see approach to aftermarket add ons is also advised...
Positives..... You can set up the exceed speed warnings if you have a lead foot, or just scan your instruments
some of the voices are funny (herbert from family guy, etc)
the map does display upcoming roads in 2D, and 3D pretty well, but set your zoom level, the automatic zoom will sometimes close in too much in urban areas.