It doesn’t warp or rot, can be as much as half the price of wood, is much lighter, and is very strong when used properly.
Of course, the first project I used them, I received my share of cuts from metal splinters, and it took awhile to get used to the way you have to build walls with it, but after that I can now move very quickly. Another advantage, at least for me, is that I can cut the stuff at 2:00 am, while the wife and kids are sleeping since I use snipers and not a noisy circular saw.
Of course, it takes time to get screwing drywall to the studs right, and you still need wood to frame closet doors and such, but you can frame an entire section for a ceiling, then hold it up with one hand while attaching it with the other.
My advice is to get a good article on the subject since framing doors and corners is different. I think there was such an article a couple of years ago in Fine Homebuilding magazine.