The great thing about the taskbar is that everybody and their pet dog have an idea for how it can be improved.
The bad thing about the taskbar is that everybody and their pet dog have an idea for how it can be improved. (And everybody and their pet dog also think that their feature suggestion is the important one that should be worked on next. Especially if it's "just a tiny little feature.")
For a few years, my office sat across the hall from the person responsible for the taskbar design and features. To help manage all the wonderful ideas that came in, my colleague maintained a spreadsheet of all suggestions that were submitted and deemed worthy of further investigation. And for each suggestion, there was a rough estimate of how much developer time it would take to implement that feature.
The total came out to over 200 days of idealized developer time.
In other words, under perfect conditions (for example, on the rosy assumptions that no earlier feature made a subsequent feature more complicated and that all the code will work the first time), it would take one person over 40 weeks of vacation-free full-time coding to implement all the little features people requested. Death by a thousand cuts. Or in this case, 200 cuts.
That calculation of course ignores the time spent designing the feature, developing a test plan, running it through usability tests, writing the automated testing, debugging all the issues that arise, doing the threat modeling, fixing the compatibility issues from applications that relied on the old behavior, and all the other things that you have to do to ship a feature beyond simply writing the code for it. (Indeed, the "write the code" step is one of the smallest steps in the product development cycle!)
Obviously, you can't implement everything on the list: You don't know what you do until you know what you don't do. (And imagine the size of the resulting taskbar configuration dialog!) But it also means that there are a lot of people with pet dogs who think you're an idiot.
Maintaining the list was a useful exercise for another reason: Whenever anybody stopped by and said, "Hey, why doesn't the taskbar...", my colleague could say, "That's a great idea. It's on the list."
When my colleague left the group, ownership of the list was transferred to the next person responsible for the taskbar design. For all I know, there's still a list sitting in a spreadsheet on a designer's computer somewhere.
Part of the hard job of product design is deciding which 20 features you have the resources to pursue and which 180 to leave for next time. If you choose the right 20, people will say you're the best new UI feature in Windows, or even the best Windows 7 feature, and they won't mind too much that you didn't get to the other 180.