Visual Studio 2015 slow
Uninstall Node.js from Programes and Features in the control panel. in addition see the following post https://stackoverflow.com/a/31655079/4446346
Make sure you don't have "maximum battery life" option on the power options.
I made the horrible mistake of enabling that. CPU never went above 5%, and the system was crawling so slow I was sure the computer kicked the bucket. Took me 2 days to realize it was the power options.
I had the same problem in the first week after I had installed windows 10 (clean install not upgrade) and now it works much better. I think that your problem is because of Windows 10, it was not completely polished when it was released but due to the automatic updates, somehow, Microsoft addressed some problems.
Also, do you mean Visual Studio Professional, Enterprise or even Community, no? because there is no Ultimate edition of Visual Studio 2015