Why I still use OS/2 (eComStation)
As a consultant, I look at computers and operating systems from a "best tool for the job" perspective. Some systems are better suited to some things than others. I wouldn't expect to play modern computer games, written for Win32 or Win64 on Linux or OS/2, no matter how far advanced Wine or Odin was/were. Likewise, I wouldn't consider running a web server on the Win32 or Win64 platform vs Linux or OS/2.
Along with other suitability considerations, I factor in my own (or the client's own) comfortability factor with a particular environment. The Mac object oriented desktop is quite nice, though it's not my environment of choice. On Linux, I prefer KDE to Gnome, but neither of those nor the Mac desktop nor Windows Explorer approaches the level of comfort, familiarity, or ease-of-use which I experience using the Workplace Shell, which is - for me, at least - the main reason I stick with eCS.
Stability concerns? These affect all platforms at one time or another. Unless the problems are inherent to the overall system design (Windows' weak security model and the dangers of the single registry paradigm), such things need to be considered in the course of business. that is to say, they happen. Cars break down, too, but I'm not quite ready to go back to a horse and cart (and carts break - ever change a wagon wheel?).