Went into the dealers today (supposedly just to drop off some paperwork, lol) and ended up playing with both new and old versions of Pro Nav 609.
Got to say, software wise they seem very similar.
Sure there are some features on the new version that the old doesn't have, but these I would class as a gimmick type thing, something you would rarely use.
For what you use it for, i.e. Nav there is little difference in the graphics and clarity, newer one being a little sharper, but you need to compare both almost together to notice.
Where the new version does shine, is, it is very quick. Going onto the older version, you get this pregnant pause between each button press. Annoying after the instantaneous new version. Destination mapping seemed a fair bit quicker on the new one too.
Verdict is, (bear in mind this is after maybe 10 minutes on both) those with the older system aren't really missing out much at all.