JagerMonkey will change that, handling the code that the existing Tracemonkey engine cannot.
Of course it will be some time before JagerMonkey makes it into Firefox proper. In fact, as of right now it isn’t even in the Firefox nightly builds. If you really must try it for yourself right now, you’ll find a link to the source code on the Mozilla wiki.
So far, the project doesn’t have a roadmap and the wiki page indicates that there are still many optimizations to be done, but when JagerMonkey finally lands, it may well put Firefox back on top in the web browser speed wars.
Photo: Wikimedia Commons, PD