If you choose a mouse over looks, then dont know what to say, having 2 side buttons one for expose all windows, one for current app windows, scroll both direction and free spin mouse for quick scroll, and a zoom button near thumb, cant think of a better mouse!
Apples no mouse dosnt evan allow expose, yes it might come in 10.6.2 but still, not going to be as easy to use. I have tried the mouse out in store and found it crap for going backwards forwards in browser, so uncomfortable. So if thats how expose will work then personally i think its crap.