The update speed depends on how much information is in the data files, plus how complicated the current location is. I've been using the full UK and Northern Ireland Navteq maps, complete with the full UK POI data (albeit only displaying parking and fuel on the live map) and 3D buildings for main cities. With text to speech enabled I'm still getting around 10 FPS most of the time. I did try running with the elevation data (which renders the map in 3D instead of on a 2D plane), but that dropped the display to approx 2-3 FPS at times.
If you check the "User Pictures" section of Deal Extreme, you'll see more pictures. I'll try and upload some shots later.
Actually, what people should be looking for is not the clarity of the maps, but the clarity of the voice instructions. My old Avensis had built-in SatNav which ran on a teeny mono LCD screen on the dash, but was good since you never really needed to look at it while navigating, the voice directions were clear, making use of adjectives.
"In 200 yards, turn HARD right, followed by a SLIGHT left."