@Tryptophan: Updating Java will not help, because Java is not JavaScript, that's a very common misconception. I didn't experience such problems although I have a very slow Internet connection. I'd say, it's probably a problem either with your browser or your internet-connection.

I'm using firefox 11.0 on linux arch.

@vitor, I'm using Chrome on Debian testing and I don't notice any slowdowns. I'd suggest you try that (even if you hate Chrome, just to eliminate Firefox as the problem), if it slows down too then I'd suspect some throttling by your internet provider.