The first language arts program I tried was Alpha-Omega's Lifepacs for 1st grade. In short, I didn't much like it. There was not a lot of substance as far as I was concerned, and it cost way too much for what it was. Fortunately, I was able to sell my teacher's guide the next year and recover some of the cost. I don't think I would try AO again for language arts.
PROS: Nicely laid out, easy to follow, no planning involved. Good for parents who don't like to spend time planning.
CONS: Not advanced enough for my 1st grader, too much busy work.