Recently I have seen quite a few issues with Office 2013 running very slowly and not being responsive.
A client had it so bad that you could type into a Word document and the text would lag about 1 minute behind. (I am not talking about the smooth type feature in 2013 either!)
Office 15 has built in hardware graphics acceleration which can cause issues when running on a slow machine.
To turn this office open any office product (Word, Excel, Powerpoint etc) Click File -> Options -> Advanced -> Scroll down to the “Display” section -> Uncheck “Disable hardware graphics acceleration” and restart office. (*See notes below*)
This should hopefully resolve the issue with Office 2013 being slow when compared with other software.
NOTE: As per the below there has been quite a lot of feedback for this issue.
Some people have had the issue where it is unchecked by default and checking it resolves the issue.
This issue occurs where it is unchecked but you have a graphics card that wants to accelerate the feature (The opposite to the above but causes the same issue). In this case you should check the box.
There have been a couple of comments relating to a recent Office update which causes the same issue I stated here 3 years ago.
You can now also try uninstalling Office update KB3114717 as listed below if the above does not work for you.
Thank you all for your feedback!