If you haven't yet played enough word-forming games to last you a lifetime, consider checking out Wordament. Previously available for Windows Phone and Windows 8, this title has now made it to the Apple App Store complete with ten Achievements worth a total 50 Gamerscore points.
Xbox Achievements on iPhone? I never thought I'd see the day! Better yet, Wordament is a free download and, truth be told, actually pretty fun. I liked the added sense of competition in the way that you're matching words in real time alongside everyone else who is playing.