Bought this set in late 2007, which was the period when I mainly referred to the book and listened to the discs. I did continue using it on and off during the subsequent couple of years, though. Eventually I decided this wasn't as good as my other Polish-learning sources and ceased to use it.
The approach didn't really appeal to me very much, as it features a lot of guess work, such as listening to Polish conversations whilst being advised not to check the book for the translations, which to me seems unnecessarily testing.
Others may well disagree, but I believe that knowing *immediately* what a foreign word/phrase means in my native tongue is more likely to help with learning a new language than listening to conversations and trying to guess what they mean.
Not all aspects of the book & discs are like this but, having not returned to them in several years, this is an point that's more memorable than others.
I did learn some new words and phrases that I had not encountered among my preferred Polish resources, though, so it was worth buying the set for this reason alone.