(Note: If you’ve just installed Mountain Lion, be sure to run ‘Check for Updates’ by clicking on the Total Spaces icon in the menubar)
Yes, it’s possible to bring back most of those beloved Snow Leopard features that Apple unwisely did away with in Lion, and – if you get them now – for free with 3rd-party apps. I’ve been hunting down a way to get rid of all the Mission Control behaviour on my trackpad, to return the app-switcher trackpad gesture, the 2-dimensional Spaces grid and, of course, Expose.
OK, so here’s how I finally got all those lovely Snow features back to Lion. You’re going to need two free tools (free for now, so don’t hang around…), namely:
Total Spaces from http://totalspaces.binaryage.com
Better Touch Tool from http://blog.boastr.net
Once you’ve downloaded these you’re half way there, but you’ve got to complete the job by setting them up properly. In the remainder of this post, I’ll walk you through how I’ve got them set up. Try it this way first, then once you’ve got the hang of it, you can tweak it to your own style. 
1. Total Spaces > Preferences:
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In BetterTouchTool Preferences:
In > System Preferences > Trackpad:
Finally, disable the Mission Control hotkeys in > System Preferences > Keyboard | Keyboard Shortcuts:
With this configuration, you change spaces by holding down ‘option’ and any of the arrow keys to move round a grid of 9 spaces (you can have more or less if you want in TotalSpaces prefs).
You see all spaces (like the screenshot at the top of the page) by holding down ‘command-option-left_arrow’.
You bring up Expose with a 4-finger downward swipe on the trackpad (note: Expose is unavailable while an app is in Full Screen mode), and the App Switcher with a 3-finger tap.
Oh, and Mission Control? Drag it off the Dock to about centre screen and release. Should you ever need it you can always go and double-click on it in your Applications folder, but otherwise you’ll soon forget it ever existed.
And that’s it — proper Spaces, Expose, and Trackpad functionality restored!