I'll add in my comments here:
I had a 98 Mustang GT, an 02 SVT Focus, and now a 06 Mustang GT as background...
As for it being Heavy, its within a 100-150 lbs of the 350Z and G35
I don't get how you can compare the RX-8 to a base model V6 Mustang, when the V6 stang starts at 20K and the RX8 starts at nearly 6-8K more
Talking about interiors...my friend had a G35 coupe and the seats where great on with really nice leather, but a big WTF on the dash...why did they PAINT the center stack silver? I though that cheap looking and kind of nasty to be found on a car like that.
Yet again the pricing thing again...a Loaded GT is about 30K (starts at 25-26K IIRC) a G35 Starts at 34K and if you load it up, goes to nearly 40K for many of the same options you can get on that loaded GT...thats a huge difference in price.
As for the interior...I'll agree with the Materials thing for the most part, but I do like the overall design of it, but it would have been nicer to have higher quaitly plastics in it...I find the drivers seat to fit me with no problems and I'm 6'2