No feature of a vehicle is too small for Ford to take a good long look at it. Case in point is the position of the windshield washer fluid nozzles on the new 2010 Mustang. Customers had told Ford that they didn't like how the nozzle were interrupting the clean lines of the hood, so Ford decided to move the nozzles to a more circumspect location in the cowl. Small detail? You bet, but Ford is devoted to getting all details right, no matte the size.
A few other customer-generated changes on the 201 Mustang include the option for bigger wheels, moving the radio antenna to the back of the car to reduce noise, a spring-tension fuel filler cap that replaces the traditional screw-on type, stereo controls on the steering wheel, and bigger storage pockets on the doors. While each of these was a relatively small change, the biggest refinements influenced by customer feedback was the Mustang's handling and interior design.
As far as the handling goes, it wasn't that no Mustang before had handled well, it was just that the higher end specialty models, like the Bullitt edition, got a lot more love in the handling department than the base level models. So, in answer, Ford took the suspension and steering designs from the Bullitt edition, as well as from Ford Racing vehicles, and implemented them into every trim level of the new 2010 Mustang. Two of the biggest changes were the inclusion of a three-link rear suspension setup which gave the rear wheels a firmer presence on the ground, and the adjustment of the springs, shock absorbers, and stabilizer bars to make the Mustang's handling and steering response more engaging to the driver.
The interior saw a lot of refinement from the previous generation as well. One of the biggest sore points for some Mustang customers was that while the interior of previous versions was certainly functionable, it wasn't exactly precision made. Some models had gaps between interior parts, and those interior parts weren't exactly made with the most appealing materials. The new interior uses Ford's Thermoplastic Olefin skin (TPO) and aluminum accents.