I almost bought an expensive Clarion head unit for road tripping with my iPod. Then I found out just what you said, scrolling and accessing your music is tedious and time consuming.
So I went with the Harmon Kardon Drive + Play unit. It's not a head unit but controls the iPod as a peripheral. The controller mounts almost anywhere. The small screen can be placed on the dash or windshield or you may be able to use your onboard head unit's display.
Scrolling is just as fast as on the iPod and this unit was installed complete for less than 500 bucks. I'm happy with it. I use a 40 Gig iPod and had given up trying to use it in the car until now.
Hope this helps.
I recently put a Panasonic CQ-C7103U into my car so that I can use my Ipod. I have discovered that while it looked good in the store when actually using it in the car the use of playlist is cumbersome at best. The unit is overall good but the only way to use the ipod is either be very creative with your playlists or get used to a very slow scrolling. Since I have a 60Gig Ipod scrolling from a-z would take hours.
So does anybody have any suggestions on better units or how to manage it better?