I really like the Office suite on Mac, though I did have a little dificulty to get used to it in the begining. some things are a lot different to people like me that has a long path on the windows version, but at the end Im enjoying the Mac version much more than the one on windows.
But also Im thinking to give a shot on the iWork suite, specially the keynote app, that I've heard a lot about. I always liked the Apple aproach on software, and you can see it comparing, for example, Entourage x Mail. even using more Entourage, since I need Exchange, I like more the Mail app that came with Leopard. Microsoft apps tend to be too much bulky, and Apple are the simpliest yet very powerfull 🙂