Yay! The day has come! Mac OS X Lion is released! Pluses include Misson Control and Launchpad, which looks a lot like the iOS devices home screens. But I'm not posting to boast about these features, which you can read about on Apple's site. Click here for some pretty pictures giving a nice overview, and click here for specifics on the 250+ new changes.
The one thing I noticed when I first started interacting with the new OS was the scrolling was weird. The two fingers up/down swipe seemed funny. Previously, swiping two fingers downward would scroll the page down. However, in the new Lion, swiping two fingers downward scrolls the page up. After a little thinking though, I can see what Apple was trying to do. I believe they wanted to set up a more universal scroll up/down action for all their devices--Macbooks, iPhones, and iPads.
On an iPad, users drag the page to reveal what they'd like. On an iPad, you would 'pull' the page upward by swiping your fingers upward to see what was further down on the page. You would use a similar motion on your iPhone. Now, the very same action is used to control your Desktop file viewing experience.
When you think about it that way, the 'reverse' scrolling seems to be a little more logical. However, the same scrolling rules apply for external mice--and I feel this change will take a little longer to get used to. Prior, I would scroll downward to go down the page, but now I have to move the scroll button on my mouse in the opposite direction. Too weird.
The next thing I noticed, was I couldn't use the finger shortcuts to move backward and forward when I was in my browser (Google Chrome!). After reading a little bit online, I found the answer. If you're interesting in restoring this nice little trick, read on.
 Open System Preferences.
 Click on Trackpad.
 Click on More Gestures. Change the settings to be as indicated in the image below. I recommend that you change all of them because you will find (if you experiment) that certain settings depend on the settings for others.
After you do this, you should regain your ability to use a three finger left/right swipe to move between pages on your browser.