if garmin wanted to a simple update would give the existing 660 and 665 owners the same route options (ie twisties) It would be the best update I can think of..
On my iPhone I have a TomTom app that turns my phone into a full featured GPS.. about a year ago I got an automatic update. After the update a new choice in route options was available. Winding Roads and then Maximum, Medium, Minimum.. Amazing feature.. Problem is I use my Garmin 660 on the bike.. :-(
Anyhow what I'm saying is I got that update for free and I'm very happy with what it does. Garmin could do the same thing and make a lot of people happy..