I thought that Apple was, and will be, much more of a significant impact than the article granted credit to, but maybe downplaying Apple was because it is so obvious of an impact.
Whether Amazon deserves any "tablet" credit may be arguable. In its infancy, Amazon merely provided an eReader, which then evolved into a richer Color LCD User Interface, that supported web access and apps. Whether the Fire HD can truly be considered a tablet OS is probably a question for further discusion, and whether the Fire HD can provide any useful contribution to the workplace (other than consuming literature) is another question. (Btw, I have a Fire, and I use it daily, but I've never considered it suitable as a workplace BYOD device.)
The impact of Microsoft, if any, remains to be seen. Better availability of Win8Pro tablets will tell that whole story, and we may not have sufficient information until later this quarter.
Having said all of that, I do agree that one of the challenges for IT in 2013 will be addressing the issue of managing the diversity of devices not just tablets, but also a half dozen mobile phone OS choices as well. The real problem for IT, however, is that none of the devices available today (save a few sporadic instances of Win8Pro/CloverTrail tablets already available) are actually manageable devices.
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