This is a very expensive app by Ipod/Iphone standards, but it is worth every penny if you spend more than a few days in Thailand, or if you work with Thais in your own country. It takes a little time to get use to the interface and how searches are done, but it is definitive in its various uses of words, both Thai and English. I used it nearly every day and stopped carrying my Thai dictionary. It does not have basic phrases, but the Amazing Thailand App, which is available for free, covers things like that, and the two apps together make an unbeatable combination.
One wish would be for a favorites button or tool since it can take a bit of searching sometime to find the exact word you are looking for, being able to tag that as a favorite would make this great app even better. The history is one way to do that, but the history was not consistent enough to be able to use it to quickly find favorite words.
It is good with a number of technical terms and with the Thai keyboard, I could hand it to my collegues in Thailand so they could type in a Thai word on the few times when they did not know the English translation. This was particularly handy when trying to identify plants in the field, including herbs.
Again, the ability to save favorites is the only thing that is lacking from my view.