Ranked in these QuestionsQuestion Ranking
Pro Lets you download Firefox... or really anything else
This is it's only purpose. This is also Edge's only purpose.
Pro System built-in browser
Browser has many system related features. With Internet Explorer you can run certain types of files, without saving them in a non-temporary directory, or you can change proxy settings via a built in Windows dialog window.
Pro Downloads well
Downloads safely, quickly, and nicely.
Pro Works great with ruTorrent
Pro Isn't a big target for hackers
Nearly all browsers use the same browser engine as Chrome, Safari, or Firefox; meaning they have the same security-holes as one of the big three. IE doesn't, it has has its own engine.
In other words, even if you find yourself on a website that tries to hack your computer: It's very likely that the the website will only be designed to hack the big three, and wouldn't be able to do anything to IE.
Pro Can fluidly stream 4k video
IE 11 can fluidly stream 4k videos on Youtube without issue.
Con Final version of the browser
Microsoft confirmed that Internet Explorer 11 (released on 2013, still bundled in Windows 10) will be the last version of Internet Explorer as Microsoft is shifting it's development focus to Microsoft Edge.
Con No browser extensions
Internet Explorer's functionality cannot be extended via extensions/plugins.
Con Not standard compliant
Con Windows only
Internet Explorer is currently available on Windows only. Internet Explorer was previously available on OS X and UNIX, but both of them have already been discontinued.
Con Problem rendering online Google Web Apps correctly
I.E. 11 has many issues with rendering Google Web Apps correctly such as Docs or Sheets. The landing pages for each has incorrect button placements and doubled icons, making the sites barely navigable.