The Mio 168 is a very nice GPS unit. The antenna is built in, so there's no charging a GPS battery. Also, the sound is loud, which is a real plus for navigation. My unit has breezed me through to a couple of job interviews now, and even my wife thinks GPS has its merits!
What it's missing on the 168 is a stronger processor (though it's adequate for GPS'ing), a VGA display, and more memory. I've got so much on mine, I tend to run out of memory. It's too bad it's not more like the MDA IV.
http://www.ppcw.net/?itemid=2229 Drool drool.
I'm using iGuidance 2; it's the best one I've tried and I like it over Destinator and PocketMap Navigator, amongst others. iGuidance produces the most intuitive routes I've seen-- it's either the route I'd have chosen or better. It also uses Navteq maps, which are better then TeleAtlas' in my area. TeleAtlas has steered me wrong many times (missing important freeway exits, for instance). IMHO, routing and map accuracy are the most important features needed in any GPS program; they're much more important than speaking the street name (though I really do like that). 3D mode is not that important either, but it's nice to have to see more roads ahead of you. Make sure your program displays the names of the streets in 3D mode too. iGuidance also could use permanent avoid-roads.
From what I've read, OnCourse Navigator needs a better turn list. I use that a lot with iGuidance. If the GPS ever goes awry while travelling, you'll be happy you reviewed the turn list earlier. I understand, though, that OnCourse Navigator seems to be better when travelling across states, so if you need your GPS to do this, it'd be a better choice over iGuidance. Just be prepared to wait forever to compile your map.
The other thing on my wish list would be a better POI database. You'd think that they could incorporate a phone book's addresses. I've only seen one company that does this (for an additional fee), but their display is bad-- the roads don't move as you travel; the car icon moves on a static map. This makes it difficult to navigate.
-- Frank