Everyone on ETS forum reminds us that a map and compass are primary for land (and air/sea too) navigation.
That being said, GPS's are amazing. With WAAS it's about 3 Meters horz. location. Most of us practice with map and compass to maintain our skills (always a good idea).
Now I have been land navigating for 30 years and been a pilot for 20 years. Even in my dreams try locating yourself to 1/8 or 1/4 of a mile by map and compass in sparse terrain. Yes in woodlands with lots of handrails, clearly defined features it's easy to find your position to 50 Meters. But under stress, in poor visibility, when your tired, etc. It's nice to have the option. Remember you can always turn it off when you want.
I personally carry at least two compasses at all times in the field, and at least one GPS. You never know.
GPS's are so cheap now, my first one was >$500 USD, and didn't have any mapping functions.

My first experience with topo charts was flying low level visual navigation in flight school. We'd layout our planned course and stay on it. We marked the chart to indicate where we should be at any given time given the velocity we had planned. In mountainous terrain, navigation was fairly easy because we could see the terrain features clearly from altitude.

At ground level, those terrain features become obscured from things like trees and brush. The "trail" you're walking suddenly becomes overgrown and then disappears, or whoa, there's more than one trail and that's not on the chart. . . Map and compass usually works, but sometimes it's nice to turn on the GPS, get a good fix of where you are really, and then proceed knowing you're on the right path.

Loading key waypoints into the GPS before the hike and adding points of interest along the way makes even a non-mapping GPS like I carry (Garmin Geko 301) very useful. The Geko 201 and 101 come in the same small package and are less expensive with fewer features.

I find these GPS receivers ideal if your primary navigation is with map and compass. They are small and light (3.9'' H x 1.9'' W x 0.96'' D and 3.4 oz) and a pair of AAA alkaline will go 9-12 hours. If you have no use for the baro altimeter, go with the 201, waypoints, routes and saved track files are the same and it gets better battery life.

Garmin eTrex Legend user here. Previously I had an old Venture model, but that lacked a built-in basemap, which can be very handy.

I find the GPS to be a great tool while on road trips and while hiking or exploring the backcountry. There is a little bit of trouble getting a position fix while under heavy tree cover, but some of the newer models with the "Sirf" chip are said to have better reception.

Once you get one you'll wonder how you got along without it. It has saved me a lot of wasted time, especially when driving/working in an unfamiliar area. Instead of having to stop and pull out the road map, I can just glace down and confirm the right direction.

For hiking it's great for giving your position, marking waypoints, leaving a "breadcrumb" trail, and navigating to where you want to be. Also, as you mentioned, it is great for giving out coordinates during an emergency.

At roughly $100 you can get a basic unit, when you start spending $150 and above you can find a unit with a built in basemap and lots of additional features. It won't take the place of a map & compass, but I see it as just another layer of preparedness. Plus, it's waaay cool. <img src="/images/graemlins/grin.gif" alt="" />