It crashes. A lot. Like, at least once a day I have to ctrl+alt+del and restart it on my laptop. It freezes and the window stops responding, it doesn't even paint.
In the inspector, the DOM breadcrumb area scrolls and moves around. It's like the blink tag, only worse.
JS debugger feels worse and clunky compared to Chrome.
Element inspector feels like duplo to chromes lego (does that make sense?)
I opened firefox yesterday and found a new speach bubble icon asking me to connect to O2 for something. WTF?! WTactualF is that all about?
/rant