Ben's branch rework has landed, improving performance significantly with the new JS engine in 10.0.2pre. This release also splits significant portions of the JS engine into G3/G4 and G5 code paths; for those of you who think the G5 sucks, don't read this blog post with more optimization notes: http://tenfourfox.blogspot.com/2012/02/1002pre-available-now-with-awesome-plus.html