I've been playing pipes longer than i've been playing guitar, and I think that its kind of disappointing when your at a gig and the only song the crowd whats to hear is amazing grace when there is a slew of more beautiful tunes out there. listen to flowers of the forest, the moreen, lexie-bex, for example. i'm just ranting and lynyrd skynyrd might feel the same way about free bird. watch a youtube video of jack lee, 78th frasiers, or field marshall montgomery and i bet they feel the same way.
to answer a few of the questions above, Great Highland Bagpipes are the most common by far(used in the AC/DC song), and their from scotland. There in the key of A, but at like 470hz, so its sounds like Bb. The notes on the "chanter" aren't on the western scale, so the notes aren't really in tune even at 470hz, but their making 440 chanters now, so that pipers can play with nonpipers. as far as difficulty to learn, I took lessons for about two and a half years until I was able to play in a band and not sound terrible. also, you have to practice fairly regularly in order to keep up the endurance to play, unlike guitar where one doesn't suffer largely from not playing for a few weeks.
sorry about the long post~