I've noticed high processor usage, especially when on Facebook.
I noticed this due to fan speedup when rendering portions of the pages.
This didn't happen a few builds ago.
Then I started keeping track on processor/core usage and noticed that Firefox uses at most 2 cores on the i7 processor. Used to be that FF was one of the fastest browsers around, now it's slow as snails, and I know it's not the add-ons as I haven't changed add-ons in a long time.
I didn't see a bug report selection in the list, so posted here.