Checkpoints, well they're alright, but to be honest, they're just ripped off VCAA questions which you can just find on the VCAA website for free, so if you're asking me if it's worth spending money to get something you can get for free, I would probably say that it's not - that's pretty much common sense isn't it?

Anyways, out of the other ones, I reckon the ATARNotes Exam Study Guide would be the best, it's definitely the most comprehensive out of all study guides and the detailed solutions will help you heaps, plus it's written by one of the best authors going around (i.e. Thushan).
The truth is, I don't think many companies will be releasing books for the 2013 - 2016 Study Design just yet, as ATARNotes are really hoping to be first off the block, but if so, I would say go with NEAP, they're generally pretty good and reputable, Lisachem is generally up there as well, I would take a pick between those two. I honestly think that NEAP books represent terrible value for money, given that you get less than half of what you get with the ATARNotes books, but Lisachem generally is quite decent value.