Ditto to David's comments!
As a lifelong Garmin user I too am biased!
However, since my beloved Streetpilot 2820 went the way of all flesh (and was then donated to Steve who got it working again and I imagine it still is and will be long after the Pyramids have crumbled to dust) and I bought a 660, I have never been down so many blind alleys, taken so many unnecessary 'long' cuts, been down so many green lanes which a m/crosser would struggle to get down, been so confused and befuddled in my entire life.
To echo Rae's comments about the routing algorithm, it seems to me that it is either black or white with no common sense thrown in.
In shortest route it will literally take you the shortest way even if no-one in their right mind would go that way.
In fastest route it will take minor road shortcuts that might shave 2 seconds off your time if you don't meet anything coming the other way, again with no common sense thrown in.
Now, I thought this was because I use it in 'motorcycle' mode even in the car. My logic is, I want to have the same information in the same place on the screen so a fleeting glance tells me exactly what I need to know.
But, I have tried it in 'automative' mode and it still puts the bloody car down places I wouldn't go during daylight hours even in my rallying days!
So, do what you will with this user's experience when the time comes to change.
Brian (who might not be too biased in the future)