While I previously resorted to JS Shell and Venkman JS Debugger, I recently had the pleasure of using Firebug. I easily managed to find some performance bottlenecks in my Online Scrabble Clone, Yabble which should be a lot faster now thanks to some great profiling features. Yabble should be slightly faster and pending some other updates I’ll be able to shave off another 20% or so from load time.