I've been using the Mio 168 for a couple of years now and it has suited me fine. It has the Travroute software and I loaded Oze CE and a stack of maps.
You can get 1gig & 2 gig and bigger SD cards now so I loaded the software onto one of these and there are no memory issues.
I must have written a million words on the system in here somewhere, so a search for Mio 168 might bring something up. Basically I like to be able to carry it in my top pocket when I'm not driving. I have used it all across Aus and in NZ too - just load up the maps for the area you want.
The Mio's archillies heel can be the inbuilt battery running flat, though I havent had too many prob's.
However, Ive just picked up one of these, which have replaceable batteries (I bought a spare battery too).
www.ja-gps.com.au/travroute_asus636mypal
They have a faster engine than the Mio, I havent loaded Ozi on yet but will get around to it soon. The old mio has been dropped on concrete a few times now and a small portion of the screen sometimes blacks out.
A question for the guys with GPS in their phones - do you get charged by the phone company for "air time" when using the GPS, or is there a chance you will in the future?
Any way good luck with it all