Migrating from Open Source SDK

I have a project that used the Open Source SDK and thus did not take advantage of anything CS4. I was recently gifted CS4, and now I wonder if things can be done better?

For example, one of my games uses some kind of phase transition to maintain state. Tons of if ( currentStep == N ) statements. Is this better using movie clips and using named frames?

Any other tips that you would recommend to a newbie to CS4 (but knows enough about AS3)?