No doubt I'm just re-stating what others have already said a million times over, but if it costs you nothing to simply put it there, then why not give everyone the choice? Personally I hate--HATE--pinning applications to the taskbar. I want my taskbar to be a...task bar--a bar containing my current tasks. Not littered with crap that I may or may not use. Yes, I know I'm contradicting myself based on how most phone and tablets function, but on a desktop, you do much more advanced tasks--which implies having an advanced interface. Why not give me the menu of all of my applications, accessories, modules, etc. in a simple start-button click as opposed to being forced to go through an impractical UI to access these items, pinning things that I might use? I can already add a shortcut to my desktop if it's REALLY that important, or a shortcut to quick-launch.
I'm mostly taken aback by how vehemently MS is against their start button in windows 8. I'm not getting how they can monetize the prohibition of the start menu any more than they could monetize having the start menu.