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I get this on my early 2011 MBP too, pretty annoying. It seems to happen in gmail a lot.
 
I guess we gotta wait for Safari 6.0.1 for the fix... It's been seeded to the developers for a while now...
 
I've been experiencing the same issues.

Words disappearing/reappearing when typing in form boxes/forums/facebook status updates etc.

Stuttering on CSS transitions, stuttering on animated objects in Safari, for example when the Facebook side bar updates and slides old posts down, it stutters alot!

Seems to worse with 6.0.2!
 
+1
Still using Safari because Chrome scrolling performance is pretty poor in comparison on my rMBP.
 
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