Many web apps leak memory on IE11 despite running fine on other browsers. We've identified two main causes of this.
The first kind of leak is simple, entirely predictable and caused by a quirk in how IE's JavaScript engine handles closures. Let's call it an “undead closure leak”. This leak goes away if you properly clean up all references or reload the page, and thus affects only AJAXy parts of the apps.
The second kind of leak is a complex permanent one, leaking the entire page context even if you reload the page. Let's call it a “GC singularity leak”. It's triggered by certain JavaScript code patterns, seemingly because IE's garbage collector never finishes its job (our theory is that it exhibits exponential complexity and encounters some sort of timeout/threshold).
This might not be an exhaustive list; internet posts point to other issues, notably when handling IFRAMEs, but we haven't encountered any of these.