USB is a good example. They added support for it to Windows 2000, and refrained from updating Windows NT to support it. By some odd coincidence (NOT), all the new retail non-USB products (including ones that worked perfectly fine with the old connections -- mice, keyboards, webcams, printers, etc.) disappeared from the market overnight, leaving consumers unable to buy anything but USB, even if they wanted to pay good money. This was a major pain point for me for a long time, and is thus seared into my memory, because NT was working great and I did not need Windows 2000, except for USB support.