One of the most interesting cases is Cisco, which implemented a BYOD-like policy in the firm. The result was happier employees and one of the biggest ramp-ups of Apple technology I've ever seen in a global company. Looking under the covers, though, this was largely because IT got out of the way of the Apple users who didn't load applications that tended to blue screen Windows boxes. It also created Web-based help systems and drove community solutions to technology problems.
The preference for Apple actually had more to do with IT, in a negative way, than it did with the differences between the platforms. The Apple users got more up-to-date hardware, more up-to-date software, better interactive tools and no out-of-date applications. This would be like the difference in experience between a brand-new car, which you chose based on your needs, and an old Ford LTD with a Model-T engine that the company chose for you with a plaid, weathered interior and broke down regularly.
The IT-based solution was horribly matched to the user, while the Apple-based, user-selected solution was tightly tied to what the user wanted to do. The IT solution was massively out of date while the user solution was current, and the IT solution was generic to the company while the user solution was matched to the employees' needs. My only surprise in looking into this was that every employee wasn't on the Apple product, which I think goes to the fact that users really don't like to learn new platforms and suggests that once on Apple, it is highly unlikely that users will move back to Windows, particularly if IT is choosing the solution without them.
Both from technology vendors like BMC, which has been driving its cloud workshop as a fix, to CIO events like EMC's, there has been one common concern and that is that users are increasingly bypassing IT and using their credit cards to buy cloud services. This is because, just like my earlier experience at IBM, IT has forgotten that it is a services provider and that its customers actually do have increasingly compelling alternative choices.
What BYOD appears to do, using both the Plantronics and Cisco examples, is put users back in control of their hardware and removes IT as an impediment. IT then can assist in this process and focus on assuring that its responsibilities to protect corporate data are met and it can be aware of the need to control and standardize the user hardware. It becomes a forcing function to recognize that users need to be given the choices that will help make them more productive and IT simply doesn't have the bandwidth to optimize tools for every user - desktop technology has evolved to a point where it doesn't really need to. It appears to help change IT from an impediment to an asset and allows IT to focus on providing cloud or hosted services to these desktops, focusing its limited resources on projects it can be more successful at achieving.
Wrapping Up: Windows 8
There is an old story my grandmother told me about the sun and the wind competing. They argued who was the most powerful and they bet on whether they could remove the coat from some poor guy who was walking down the street. The wind blew and the harder he blew the tighter the man held on to his coat and he failed. The sun gradually increased the heat and the man eventually removed his own coat. The lesson underneath the story is that finding a way to encourage a behavior is often more successful than forcing it and given IT has little real authority, as cost center staff, organization-building support could go a long way to assuring IT meets its objectives.
If you look, I mean really look, at Windows 8, more than any other OS, because it blends tablet and laptop concepts, lends itself to a highly user-focused solution and works horribly on the typical IT cost-optimized laptop, it will be unacceptably limited to most. Not only could IT's status depend on making the right decision, the entire future of Microsoft and the PC industry could be tied to doing this right.
Sometimes the best decision is to let someone else make it. Increasingly, with cloud services enabling the user to do this for themselves safely, it will likely be the most successful path for IT.
In any case, and this is true of any service provider including IT, if you become a barrier to the folks who own the budget, eventually they'll stop funding you to eliminate the problem.