seobook v seomoz rank checking tools for me in terms of quality, usability and accuracy currently falls to seomoz!
Eventhough I am a fan of the client based app which is what seobook has, well a Firefox Add-On, seomoz’s online tool just works well and gives a ranking history in a graph style format, seobook’s tool just needs an upgrade, seems a bit clunky, sometimes unresponsive and the position accuracy in the data returned is a wee bit suspect, maybe it’s just the OSX Firefox version, haven’t tested on a WIndows environment yet.
Must admit i have been testing another one which i will save for a future post that really is great and quite frankly kicks butt!