Here is a shameful confession for a Mac user/cultist: I've almost never used Expose. It is, I know, a great concept, which many people have come to rely on. As someone who keeps far too many applications running and windows open at once, and who sometimes gets frustrated looking for the right one, I ought to be the target market for it. Yet the implementation never quite felt natural to me. My pointer always seemed to find its way to the hot corners unbidden, irritating me often enough that I just turned them off. And I never did quite get the hang of using the function keys for this purpose; I'm a pretty a good touch-typer, but if it's a key that wasn't in the keyboarding class that was taught in my senior year of high school, I haven't been able to develop a feel for it. I ended up sort of stabbing at the area of the keyboard where the Expose keys lie, with middling results, and quickly gave up on that too.
The biggest problem, for me, was that there was no obvious connection between flitting my mouse to one corner of the screen and/or pressing one of your higher-numbered Function keys on the one hand and doing the nifty UI stuff Expose does on the other. True, pretty much all interactions you have with a computer are arbitrary to some extent, but I had a hard time making this particular connection.
And now, thanks to the modifications to Expose in Snow Leopard, I don't have to. The bit of Expose functionality I always found most tempting -- to have all the windows of a single functionality available at once -- can now be invoked by clicking and holding on that application's icon in the dock. That's the sort of connection between on-screen graphic and conceptual action that makes sense to me, and that feel typically, well, Mac-y. It's still something I have to sort of consciously to add to my workflow -- old habits die hard -- but it's becoming more instinctive as the days with the new OS go on. It's pretty much worth the $29 by itself, as far as I'm concerned.