users. Let the users tell you what is good and bad. Build the interface to match the user.
The interesting thing here is that your evidence doesn't match the examples.
Microsoft puts every single thing they do in front of users, and tests it to death. Apple puts some really smart, good designers in a room and they do what they think is best. (overly simplified, but you get the idea)
One of the first things Jobs did when he came to Apple was to kill the UI research group. They have a unified, attractive and logical interface because they keep it tightly controled and don't let groups of just anyone come in and tell them to change things. They're also secretive to the point of paranoia, which means they'd never be able to do user testing groups before launch of anything.
Microsoft is bland because every single thing they do is tested over and over and over again with user groups, which gives them a lot of data, but means they end up with the lowest common denominator on everything.
You can make your own decision on which is better.
I actually read something that made the case that Microsoft was too consumer focussed. This is around the time when MS had just got the security religion and the person said that until then, nobody was asking for security in their focus groups and market research, just features and compatibility with older software. Geeks were asking for security, but they made up a relatively small number of people in the market. When worms,viri and root-kits and all that started being more and more prevelent, people started asking for security, and so MS started doing security.
Short version: Ask your users what they need all you want, but you're always going to be a reactive organization, and you're never going to surprise anyone, because they'll always just get what they ask for. If you make educated guesses what they need, you'll sometimes blow them away with something awesome.