I've detected a bug in RSyntaxTextArea:
symptom: Very very slow scrolling
affected OS: only Mac OSX (I've tested on Snow Leopard an Lion)
1) Open some document (scrolling is fast)
2) Type some character
3) Now scrolling is super slow
As far as I've been able, I've tracked it down to the code folding feature. When disabling code folding, the bug isn't present.
I've also tested on Windows XP where I was not able to reproduce it.