I've cooked with it and made it from scratch. It can end up a lot less dense and not as evenly textured when homemade, at least in my experience -- I'd buy it premade and see how you like it, first. I've only made fairly traditional versions -- it's fun to make, and a lot cheaper, but I rarely take the time.
Aside from using in stir-fries, probably the thing I do most with it is that I'll buy "chicken-style" (which basically means no soy sauce) for fajitas -- marinate in tequila/lime along with portobello mushrooms, sautee with onions and peppers, serve with usual fixings. I also really like the traditional stuff just sliced and cold on sandwiches.
Yes on both counts! These recipes, for seitan sausages and a basic seitan blob, are awesome:
I buy seitan based sausages (Fieldroast) and seitan occasionally, but it is much cheaper to make your own.
I like seitan sausages plain with sauerkraut and mustard on the side or sauteed with greens and served over pasta. Basic seitan from the PPK recipe I slice and stirfry with vegetables. I want to try making lunch meat with this recipe, but haven't gotten to it yet.