@missalina; an antagonist cycle is a short cycle (yay!) where you start your stims a few days after CD1 of AF, then a few days later you start orgalutran (which stops you ovulating).
I take a while to stim, so I'm usually 12-14 days of stim injections but it's all over and done with about 2-3 weeks after CD1.
A long down cycle has you on the pill for 2-3 weeks from CD1 or 2 of AF, you then stop the pill and start lucrin (I think you can use other inhibitors, but lucrin is the one my FS uses) and then a few days later you start stims. All up it's about 6 weeks from starting the pill to transfer so it seems like forever! A long down cycle is usually used for older women or those that don't produce many eggs/get cysts etc. It's something about shutting down the ovaries first.
I've done 2 antagonist cycles and two long down cycles, not really sure if one worked better than the other!