What browser are you using? That usually is most of the problem. Chrome chews through even the toughest javascript-based apps, including gmail, greader, facebook. It's way faster to load a web page than to open an application on my own machine.
I have 10,000RPM drives in RAID 0, so my computer is always faster to open a local app than to open a webpage.
For example, I've seen several websites that crash Linux in Firefox -- not good. The rendering in general is also not as good as win/mac, esp. with respect to transparency.
Haven't had any crashing problems, either.