I'm looking at new cars since my current car is getting long in the tooth and expensive to maintain. I'm looking at 3 cars primarily: 2009 M3, 2008-2009 Porsche Cayman S and the 2013 Boss 302.
What has your experience been with the Mustang in terms of reliability, build quality and overall experience? I'm not expecting BMW interior quality in the Boss 302, and I've looked at the 2013 model to see and confirmed my expectations. The fit and finish is good and tight, but the materials were cheaper (expected). My question is, how long does the interior stay tight? Do they develop rattles and squeaks like I've seen in older Ford/Chevy/GM vehicles?
What's average for maintenance expense? I'm expecting it to be way cheaper than my current 2006 M3 (older bodystyle), but that's not a hard bar to beat since I am spending $3k+ per year on maintenance...

Which is a big reason I'm considering going with a Boss 302 rather than a BMW or Porsche.
One of the things I love about my current car is the ridiculously balanced handling, which I may lose going to the Mustang vs. the M3/Cayman since it's got a live rear axle rather than independent suspension. Has that been as large a factor as it's been made out to be? I know they've made good times around tracks, but I expect that's due to the tuning and professional drivers that make up for deficiencies and may mask handling differences between cars. That said, handling is one of the most difficult factors to gauge between cars and can't be determined on a test drive (unless you've got a crazy salesman).
Any other issues I may not be aware of, such as rear visibility? I'm looking to buy within the next 1-1.5 months and would greatly appreciate input from those of you with experience with the Boss 302.
Thanks for reading!
-Brian