I've been going to MINI of North Scottsdale since I bought my first MINI Cooper from them in 2006. I'm on my second one (a 2011 MINI Cooper S Convertible bought in October 2010) and the buying process was smooth, hassle-free, and low pressure. I've bought a number of cars, both used and new, and MNS is easily the most pleasant experience I've had.
Their service has improved considerably over the years. I love MINI's three-year, 36,000 mile maintenance warranty and MNS makes it even better by over-delivering. Their prices outside the warranty are higher than I'd prefer, but I really don't know if they're more than I'd expect. They've started using MINIs for loaners (love that) and fully comp the rental if you have to go to the on-site Hertz or Avis (can't remember which) when they don't have any MINIs available. (They used to make you pay a flat fee of $9.95 per day so getting rid of that is just great.)
One time I had service and needed a loaner. The loaner's gas tank was not full and I ended up having to spend $15 because I hadn't noticed it until I left the premises. I was pretty upset about it and Matt really wowed me when he made it right.