Just my opinion, but I don't think 401A is worth it (the interior w/ accents color you speak of.) MAYBE if the accent color by definition matched (or at least as far as leather dye can match paint on steel) the exterior paint. Otherwise to me it looks tacky.
Also don't like the bright shift knob. (Not really a good grip, and too hot in summer.) And the dash "carbon fiber" looks cheap compared to the regular Premium aluminum.
Finally, Mustang seats in general are nothing to brag about. They're nothing compared to our 2008 BMW M3 - no real surprise there. But they also pale in comparison to ... believe it or not ... the 2007 Jeep Wrangler I currently use as my own daily driver. That will be one tiny disappointment when I trade the Jeep for the 'Stang.
Don't get me wrong - I am TOTALLY STOKED to get the new Mustang, I expect to love most everything about it, and, especially when price is concerned (and maybe even when it isn't) might wonder why we ever spent the money for an M3 in the first place.
Hell, if I could foresee the future, I might see us trading in the M3 for a 2012 Mustang. But that will be up to the other half...