I have a Great Pyrenees named Bruin. He is 11 years old now, and has always been a wonderful calm mellow boy and an absolute joy to have around. It really depends what youre looking for in a dog though. Their breed is historically Livestock Guardian, whereas shepherds are Herding Dogs. that means that Pyr's were meant to be left alone in the mountains with a flock. Whereas shepherds were designed to WORK, and work WITH the shepherd, taking cues from them. So Pyr's are generally more independent, and dont quite have that constant eye on the master, eager to please thing that shepherds usually have. They also dont have as high of an energy level as shepherds.
My guy has basically never had a prey drive. He's never been much of a chewer, doesnt understand toys, wont chew on anything that isnt food. I dont think the chewing thing is necessarily typical to the breed, but i think the prey drive thing is somewhat.
As for the coat, yes, there's a lot. lol. Its not really bad for the first two years, but i highly recommend making brushing a frequent activity as puppies anyway, whether it seems necessary or not, because its not so bad to brush them, unless they despise it like my guy does! lol. They will develop a very thick cottony undercoat, so your best friend is a good rake. Well, two, one for the undercoat, and one for your lawn after you're done brushing! Haha.
It's not that bad though, if the dog is cooperative. But the full body workout my dog puts me through to get him brushed has me molesting every greyhound that comes in the store I work at (feel that smooth short coat! Ahhhhh......)
I adore their calm mellow gentle personalities though, I really do love the breed. I couldn't imagine a better match of a dog to my personality, but my kids are always jealous when other people's dogs are playing fetch (Bru doesnt) and I know my friend who is all about her dog obeying her every command, would be very disappointed with Bruin's "in a second" attitude.
Training plays a huge part, I'm sure a pyr could be trained to do anything a shepherd could do, it just might take a tweaking in your approach with different natural tendencies taken into consideration.
One last thing, Bruin has a nice deep low manly bark. Shepherds i've found have a much louder sharper bark. It's just a personal thing, and its probably a tolerance i've built up, but I hate the sound of any dog's barking, but I don't mind Bruin's deep woof. I still make him shut up, lol, but it doesnt kill me. Every other bark just pierces my chest when I hear it.