The classic horror-stories-from-the-software-trenches site Worse Than Failure has a great story today about a state-of-the-art POS (no, no, it means "Point of Sale") system that, in order to make the customer happy, had to be modified to be as awkward and clumsy and buggy as the original system it was replacing.
The retailer agreed, but only to a point: They would buy new hardware and software, but it had to look and function exactly like the old systems. No touch-screens, no graphics and no cashier-friendly reminders; just a plain old text-based interface with obscure keyboard commands for navigation. After all, they had spent a lot of money developing training programs for these registers and had no intention of simply throwing them out.
This is an extreme example of a common problem in rolling out new systems to replace existing ones: even if the older systems have problems, procedures and even organizational culture can be built up around these problems, and removing or changing them can be dangerously disruptive.
In this case, they had designed the system first and then got feedback from the customer after they were finished, which is often a recipe for disaster - as it turned out to be. However, one way to approach this situation would be to have it be able to support the older way of doing things, but also support the newer better ways. This makes for a messier system, but it allows you to keep the stodgier customers happy while allowing them to move forward when they want to - if ever.
Part of the problem with Windows (and it seems that this was a big reason for why Vista wasn't as revolutionary as originally planned) is that it still has to remain backwards-compatible with thousands of old enterprise systems and SimCity for DOS. Apple has been a bit more forceful in its upgrades, but has generally provided more-or-less transparent emulation layers for a few years whenever they switch OSes or processors.
I remember training people in early versions of MS Word for Windows back in 1994, at a company that had been using WordPerfect 5.1 for DOS. The senior people who didn't type very much liked the new WYSIWYG display and WIMP interface, but the clerical staff hated it. They had become very used to all of the keyboard shortcuts (remember CTRL-SHIFT-F7?) and were fast and proficient in getting around the limitations of the plain-text-and-tags interface - now they had to relearn everything and use the mouse more, which slows everything down.
I know what that's like - instead of state-of-the-art development tools, I mostly use a 30-year-old text editor that stays fast and out of my way - and when I do use more modern tools, I make sure to enable the emulated keybindings so I'm comfortable.