The Real Solution to bring back Swiping to Lion
This (previous post) is a hack to get Vertical swiping back on the Magic Trackpad and doesn’t work for a laptop trackpad.
For this fact I think Apple’s intention is to use the Option key as a modifier to activate vertical swiping and it is likely this hack will be fixed at some point.
So my suggestion to get swiping back in your favorite cell-based apps like Carousel, Reeder, Twitter, etc is:
Left/Right Swiping

This will give you 3-finger left/right swiping like you were used to in SL (and maintain the nifty 2-finger peak-at-your-previous-page in Safari)
Up/Down Swiping

Up/down swiping will activate when Option is held down and when the Mission Control/App Expose gesture is performed. So pick which one you like the best, 3 or 4 finger. Not ideal if you are used to the way it was in SL, but like reverse scrolling, you’ll be OK.
HOWTO: Sync Carousel saves/recents with Dropbox

Like most Mac apps, Carousel stores support files in the Application Support directory, this of course includes the file used for saves and recents. You should be able to just copy and paste the commands after each step in your Terminal application…
First quit Carousel and backup your file in case something goes wrong:
cp -r ~/Library/Application\ Support/com.mobelux.Carousel ~/Library/Application\ Support/com.mobelux.Carousel.Backup
Now copy the app support folder to Dropbox:
cp -r ~/Library/Application\ Support/com.mobelux.Carousel ~/Dropbox/Other/
Next you want to delete the support folder:
rm -r ~/Library/Application\ Support/com.mobelux.Carousel
Now for the Magic, create a symbolic link that contains a reference from the shiz on Dropbox to the shiz that Carousel is looking for:
ln -s ~/Dropbox/Other/com.mobelux.Carousel ~/Library/Application\ Support/com.mobelux.Carousel
Repeat steps 3 and 4 for each Mac you want to have synced saves and recents.