Editing makes a pretty big difference to some pictures - particularly underwater photos, and photos that were over or underexposed.
Here's an example of one of our pictures from the summit of Mount Kinabalu (you can click to enlarge). On the left is the original, unedited picture. The center panel shows the result of increasing the brightness on the JPEG vs increasing the brightness on the RAW in the final panel. All that I did to this picture was increase the exposure.
|Original, edited JPEG, edit RAW|
|Original (left) and edited (right) version picture of a jellyfish|
Laura's has a copy of Adobe Photoshop as well. Photoshop is a lot more sophisticated and works on a per-photo basis; it doesn't have any of the album management features that Lightroom provides. If you do decide to start shooting in RAW and you're looking for an easy way to organize and edit your photos give Lightroom a try (Adobe offers a free 30-day trial)!
PS. Thanks to Marta and Kim for suggesting Lightroom to us (and convincing us that shooting in RAW is worthwhile).