I bought mine 15 months or so ago now (Navman F20), not a huge amount has changed from what I can see.
Basically at the time I didn't want to spend a fortune and at the end of the day I just wanted it to be clear and precise rather than have all the extra stuff like camera, voice directions, bluetooth, make phone calls or whatever other stuff was on offer at the time.
It has not failed me once and has spent a great of deal in the car as well as other cars for various interstate trips.
Downsides after all this time, it is a little on the slow side to startup and get a fix on the current location but no huge biggie, you know the general way to go so it will catch up in a few minutes, worst case scenario you have to do a u-turn.
Other than the above it would be nice to have a bigger screen but having said that I rarely use the screen once programmed and only really listen to the voice commands when prompted.
Out of the big brands Navman was about the cheapest and to this day I'm glad I purchased it.
I hope this helps.
Cheers
Darren