If you're serious about playing go, buy this app – SmartGo Kifu Review

It may seem a bit expensive, especially when SmartGo Player is less than a quarter of the price, but it's worth it. The biggest advantage is the ability to review your previous games, which is the best way to get better. Plus, it can receive SGF files (records of go games) from other apps on your device, by copy-pasting a URL, through email, and through copying-pasting the text of an SGF file. So, if you've got another go app, and you can get SGF files from it, you need this app! What's more is that the actual, in-game review features are well implemented, too. If you don't need or want to look at the text notes, you can just drag the upper handle to the top. Do the same thing on the bottom to hide/show variations. You can decide just how much space the two take up, too. Additionally, you can zoom into and out of the game board.
Review by kc9hzn on SmartGo Kifu.