MS did not fail by removing the Start button; rather, they failed by not replacing its functionality.Not trying to restart this debate, but why cant your customer do what they do on their android or Iphones- get an app for that. There are a bunch of FREE apps that bring you the start menu functions. yikes. I have one I am using called POKKI. not that I use the start button, but out of curiosity I grabbed it a few months ago because it was touch optimized with tiles etc. Works fine. TO BE CLEAR I like the start button on the 8.1 prev as is and have not loaded pokki on to it but when I boot back to 8.0 on occasion I use it the same way MS has it to access the start menu. That said your customer can set it directly up to act as the old start menu - why do they need MS for that?
The Start button provided basic and fundamental functionality to organize/group and launch Windows programs. This has been the case for years. All sorts of documentation (corporate and commercial) have been written to the tune of, "Press Start > Programs > ...".
Then MS--in all of their brilliance--decides to go ahead and remove the Start button. Okay, fine, but what is its replacement? The Start screen? Absolutely not! Until I am able to create a nested folder structure to group my apps on the Start screen, then it certainly is not a replacement for the Start button. Had they done that, then at least you would've still been able to recreate your Start button menu structure on the Start screen and then your documentation would then be more easily updated to something like, "Press the <Windows> button > Programs > ...". Transition would have definitely been much more seamless because rather than clicking the Start button, for example, you would just click the Windows key (physical or virtual via swiping/mouse-pointer-in-the-corner-positioning) and then you'd have access to the same structure you were accustomed to in previous versions of Windows.
The thing about the Start button was that it was--and is--used for basic Operating System functionality: Organizing and launching applications. Were I in charge at MS, I would not have implemented that thing they call a "Start" button, even though we all know it is not the same as the old version. Rather, I'd improve the Modern UI and the Start screen so that they provided the equivalent functionality and I would leave the Desktop Start button functionality to third-party vendors.
Much as I love Windows 8 and the Modern UI, I also see an incompletely designed UI that does not take into consideration and replicate (in an equivalent fashion) the UI functionality of billions of legacy apps and the OS itself to which users have gotten accustomed. As an example, clearly, when they released Windows 8 and the Modern UI, there was no Modern UI Folder Tree UI object. You see and experience the result of that on the Start screen, by not being able to organize and structure apps into nested groups; and also in IE, where they didn't have a Favorites folder structure of all your Favorite sites.
Overall, as an individual user, I have adapted, moved on, and love Windows 8 and the Modern UI and don't need a legacy Start button. However, because MS never fully replaced this basic of Operating System functionality with something in their new UI, then I side with the masses for their complaints and request for changes.