Sick of my tweens not being smooth. What is the secret?

Question

I am not understanding why a simple alpha tween is staggering
my processor every time and just making the tween seem slow and not
smooth.
I basically have a black movie clip that covers my screen,
and i want it to fade up. I've tried using mctween for this and on
the timeline, and it doesn't seem to make a difference.
the fact that it's large shouldn't really matter, cause it's
all vector.
i feel like on some high end flash sites, i see really nice,
smooth tweens all the time. But why is it that mine seem so far
away from that?
I've looked at cacheasbitmap, but is that the answer? My
frame rate is 30...and I don't have all sorts of animation at the
same time.
What are the tricks to get just really smooth tweens?
Thanks.

Answer 1

what if you just use a plain vanilla tween:
import mx.transitions.Tween;
var myTween:Tween = new Tween(mc, "_alpha",
mx.transitions.easing.None.easeNone, 100, 0, 1, true);