Yeah, for just something like Itunes it would be ok, though trying to use the Itunes software on a 7" touchscreen would likely be a pain since everything would be so small.
That's the really good thing about a windows based system, there are many front end programs designed for in car use on 7" touchscreens, many of which you can completely customize the looks of it, the one I used on mine does MP3's, DVD's, GPS nav, picture viewer, video viewer, can auto sync it's database with my server PC thru a wireless NIC card and I customized the program so the display matches the headunit in my car. you do get a lot more hardware options too with a windows based one.