Well, I know this is a bit sad, but I have an old Navman, (my first SatNav) a TomTom on my PDA and a new Garmin (the most recent TSV).
The Navman was wonderful when I first had it, but is now past it (they age very quickly!)
I couldn't get on with the TomTom at all.
The Garmin is WONDERFUL. I would heartily recommend it.