64-bit Windows builds, finally! This is great news. The rate of (virtual) OOM crashes on Windows is pretty high because a 32-bit address space just isn't enough for many workloads these days, and 64-bit builds solves that problem definitely.
64bit will open more address space but it has proven in the past to slow the browser down, the wider memory pointer size has a detrimental effect, Waterfox is Firefox recompiled as 64bit and other compiler optimisations: http://www.networkworld.com/article/2185649/applications/fas...
Not everything should be 64bit.
This is with tree style tabs, which makes browsing so much more efficient for me that Firefox is the only viable option.