The two crossword puzzle apps include Eliza Block's 2 Across [$5.99, App Store] and Stand Alone, Inc.'s Crosswords [$9.99, App Store]. Readers may remember Eliza Block as the part-time developer who was surprised to find out exactly how well she had been doing with her application sales.
In the end both applications are remarkably similar in execution and functionality, and you are unlikely to make a bad choice with either app. Both applications offer an almost limitless pool of downloadable crossword puzzles as well as access to subscription NYTimes puzzles. At the risk of oversimplifying, if you are a frequent crossword puzzler, Crosswords' landscape view may be worth the additional money if you dont plan on using the hints as often. 2 Across, however, is also a very capable version, and does offer a few additional features for amateurs, such as letter-level hints and Pen/Pencil modes.