A GPS is a convenient device. There's many models that work well under tree cover and in canyons. You can get a decent unit such as the Garmin 60Cx that's small, lightweight, reasonably waterproof/durable and runs off standard AA batteries for over a day, for under $200. I personally wouldn't go into unknown terrain without one.
A GPS is good for tracking your progress, maintaining a breadcrumb trail to your origin, getting a position fix where there's no discernible landmarks, and finding the nearest "civilization." You can also use it as your primary navigation tool, but I recommend against it because map and compass navigation is an important skill. It can also make for additional fun by using it to Geocache. And if you do get lost or injured but have cell phone service, it can help rescue teams find you more quickly and accurately.
That said, there are three rules to planning for back country trips: Redundancy, Redundancy and Redundancy. As others have and will probably warn, a GPS is an electronic device and is subject to failure, and the more stressful the situation, the more likely it seems it will fail. Batteries can run-out, it can be dropped and broken, or might just stop working for no reason. And unless you get a very expensive model or buy/find and install more detailed maps, a GPS will not provide all the terrain features you have on a good 24K topo map.
Since you already know how to use a map and compass, adding a GPS can be a handy and fun addition. Just don't leave the compass and maps behind. I always carry two compasses (a type 15 and a small, wristband compass), two sets of maps (topo plus a copy of the topo with my planned route highlighted with notes), along with the GPS, and will switch back-and-forth to make sure I keep my map navigation skills from getting rusty.
So there are some worthwhile benefits to carrying a GPS while camping, but not to the exclusion of a map and compass.