evilpie posted some numbers below: http://news.ycombinator.com/item?id=5227841 and I'll reproduce the salient points here:

               odin (now)  odin (next)  sm      v8  
  skinning     2.80        2.46         12.90   59.35  
  zlib         2.02        1.61         5.15    5.95  
  bullet       2.16        1.79         12.31   9.30

https://bugzilla.mozilla.org/show_bug.cgi?id=840282