I read through the thread and just for a clear discussion: Keil (not Kiel btw

) uVision 5 is the current version.
In the end what counts for me when deciding to put down money on such a product is what it costs vs. what it will solve. For example I bought a professional license for Altium because I want to focus on my job and don't want to tinker with the tool's inabilities and quirks. Not to say Altium or in this case Keil, IAR, GCC or Rowley tools don't have quirks, but when I run into a problem I pick up the phone, or if less urgent send a mail to the support team and they respond to get me going.
Be aware that costs you a yearly support fee. But for a company that should be next to nill compared what it costs if an engineer can't continue their work. Or for example when errors are made or overlooked due to characteristics of a certain tool.
That's also the way to sell it to the boss or CFO. It's an investment to gain in the end.
I'm a more of hardware guy, so if I really needed to spend a lot of time on firmware development I wouldn't hesitate to aquire one of the mentioned IDEs and look for middleware libraries that are proven and have good support.
In the end it's your own opinion that matter a if a certain IDE works for you. So again: do test them.
On a final note, it is true that I do see a lot of MCU vendor provided example code and demos that have at least a version for Keil next to the vendor's own IDE.
edit: typos (stupid autocorrect)