Firefox, 64bit nightly user here.
It's still atrociously slow, atrociously. Infact there's a either a bug with one of my plugins or something but I've deliberately endured it for nearly 8 weeks, hoping my feedback data is going in the bloody logs somewhere to help.
I run about 6 or 7 plugins which are all fairly common and I have run the same ones for 3 to 5 years. They worked fine on my last profile rebuild but this most recent one was broken /out of the gate/
It's so bad i'm using chrome primarily. Firefox performance frustrates me absoloutely no end and I've been running e10s, 64bit nightlys now for over 6 months.
Infact, except for the last 4 weeks, the ironic (?) / odd thing is, nightly has been RIDICULOUSLY stable for a piece of nightly code. It's just plain stable. It's just slow as heck.
I don't know what idiot legacy code is in Firefox but they seriously need a scrum or party or a bonus or something and the whole fucking team *STOPS* for 3 weeks solid and focuses on NOTHING but performance, performance, performance.
If you check my slashdot post history, I've been whining about Firefox performance for over 3 years.
It's ridiculous, stop adding features, just stop. Make the damn thing fast. Because Chrome destroys firefox and I'm now running a HEAP of Chrome addons (which I never knew existed) to replicate my Firefox functionality and I'm very, very close to full replication now (Firefox: Tab Mix Plus is bloody hard to replicate, requires multiple poor addons to be configured right)
Seriously, just stop whatever is going on Mozilla devs and bring in "The Carmack" or the equivalent at coding. Scrap something old, I don't care but something is fundamentally wrong when a 24GB memory, quad core machine can run so poorly with a browser.