I really like the look of Apricot Hill. It looks like a real American road course. (as opposed to the vegetation-free wasteland at Laguna. The esses kind of remind me of Road Atlanta. The blue sky with whispy white clouds reminds me of an autumn day at Brainerd Intl Raceway in my home state Minnesota.
Complex String has that same pretty sky, but it doesn't make up for the lack of scenery.
Trial Mountain is quite nice but so improbable as a real racetrack with all that exposed rock.
I was playing the Playstation III Demo machine at Target the other day and doing a time trial on the GT HD demo. The mountains were awesomely awesome.