On a couple of posts I have read how CoolBook is an absolute godsend!
I have been looking into it...
My main issue is a heat problem when watching youtube videos.
When I buy this program can anyone give me their optimal settings for a cooler MBA when using YouTube.
Thanks!
The nature of Coolbook is that it takes advantage of the fact that all chips have different tolerances and the default settings use by Apple are conservative (reliability over heat and power consumption).
So the only "right" way to use Coolbook is to choose a setting, run a stress test, if stable, save, ratchet down, repeat until you arrive at an unstable setting and ratchet it back up a bit for reasonable reliability. Each chip is different so you really can't use settings from other people other than to possibly reduce your number of iterations.
This looked like a long tedious process and not without some risk (do a search on what folks managed to do to their machines when things went bad - a small but non zero probability) so I never did it myself.
Coolbook may help with overheating and core shutdowns if you are suffering from them but it will not stop your machine from heating up and your fans speeding up when playing video. Some folks report better battery life too. Its all in how you end up balancing your system and how much leyway your particular chip has tolerance wise. Every MAC I've owned heats up and fans go faster when playing video and the MBA is no different in that respect (although its extreme thiness makes it worse). The price you pay for thin and powerful.
Try Click2Flash if you use Safari as your browser - it plays utube video through Quicktime instead of Flash (much less CPU intensive). Also the latest version of flash player (beta) is also to be reported to be better. Finally try VLC for general video use - its a lot lower overhead than Quicktime and plugins like Flip4Mac.
Good luck