almost every nokia i have owned has suffered from some kind of design flaw that has made me hate using the phone over time.
Try using some non-Nseries S60 models, you'd be surprised by how good they are now.
Do they do any type of marketing research or do they actually listen to their customers?
It sounds simple, but in practice this kind of research is notoriously difficult to rely on, especially in something as varied as the phone industry.
If it was as simple as that, every phone made by every manufacturer would be a hit. The problem is that there is no amorphous mass of "customers", there's millions of different people who all have slightly different priorities. On average the readers of AAS probably have a totally different set of priorities to the majority of people who buy these devices.
Which of these priorities you pick, who you listen to and who you don't listen to, is very difficult to judge. You can try making a compromise, but compromises are equally notorious for pleasing no one. It's probably the case that to make a successful product you have to annoy at least some of your potential customers.
I agree the N73 feels very tacky, yet it's sold incredibly well, whereas other similar models with much better build quality have been left in its shadow. Personally, as I keep saying, I think the numbered S60s are much better phones than the Nseries S60 models, yet the numbered S60s receive virtually no attention compared to Nseries. It's as if the success of a phone depends a great deal on factors other than the phone itself.
There's a famous saying about Hollywood, which comes from the fact that no matter how good the director, actors or scriptwriter, no matter how much research they do with test audiences, no matter how much money they pour into a production, no one has ever come up with a guaranteed hit film. The saying is: "Nobody knows nothing".
Going back to phones, the example that always sticks in my mind is when they revamped the original N-Gage into the N-Gage QD, mostly to answer the critics of the original. Amongst other things, gone was the sidetalking, and you held the QD right up to your face like any other phone. You'd think this would receive universal praise, but at least one reviewer slammed this change because he didn't like the way his beard got the screen greasy. Should Nokia have listened to him?