Efficiency of fades/alphas/easing and sites

So here’s my site: http://matthiaslot.com

I’m having issues with transitions easing/alpha and making it look smooth and good.

Another site of mine: http://burchettproductions.com

How does a site like: http://2advanced.com/flashindex.htm do all the complex loading and make it so smooth?

I’ve tried MM’s tween class and laco’s tweening class. laco’s improved some but site transitions/easing hang on both pc and mac.