It is hard for me to answer this without spending half the day writing this message 
There's people which hates changing their chair's height. There's people who hates you take his car and change the mirror position. Well, I hate my code being reformatted 
To me, correctly formatted code is as important as the code itself. I've been writing code for 30 years, 25 in C-like languages. I have my own style, which is not very different from a standard style. But now imagine that you've coded with Turbo C 1, 2 and 3. Then moved to Borland C (can't remember its versions). Then to rhide and several other free IDEs. Then took Visual C 5, move to Visual C 6, and started with Visual Studio 2002,2003, 2005, 2008, 2010, 2012 and 2013. I've had no problem with any of these.
And then appears 2015, and each time I edit one file created in one of the 14 IDEs I've listed, the code is refformated because somebody at Microsoft has decided my custom format is not good enough and I can't even modify the IDE to match your style. And you don't realize typing a # reformats your whole code, then you commit, then you've messed up your mercurial "annotate".
To me, every code editor must have two features:
1) don't touch my code (if I don't want you to do so)
2) never get in the middle, so that using that editor takes more time than doing using i.e. notepad.
VS2015 constant refformatting under their desired rules (some of which can't be disabled) does not comply 1.
And for 2) something as easy as using no indentantion inside a namespace... Smart indentation will stop to work properly and each time VS refformats your code you'll end up unrefformatting it. And then you'll realize you're spending more time fighting VS2015 and coding.
To put an example, take this github entry
with the Entity Framework piece of code.
This code is beautiful, clean, well indented, states clearly the purpose of itself and... impossible to keep correctly indented with the current VS2015.
Now imagine 50 statements like that in a file. And now imagine a simple '#' can "destroy" the formatting of the whole file.
Or that when writing this kind of code, each time you press 'enter', you have to adjust the tabulation manually because VS2015 thinks you're not writing the code correctly. (despite the fact that I've been using that feature since Borland C 18 years ago without any problem). It's kind of going backwards...
If you use code in VS2015 the way the insiders decided then VS2015 is probably far better than VS2013. But to me, it's hell.
And I won't mention anything about the light bulb because I could start ranting and not stopping until the PS5 is out
sorry for the giant rant, I'm a grumpy coder and you'd better not touch my code
