I love this book! I've been working through it slowly for a number of months. I think it has just the right pace and it explains some of the difficult grammar points very succinctly without trying to dumb down. The exercises are well thought out and do a good job of making the information stick without being too boring. The audio examples are excellent and as far as I can tell they sound very natural which really helps to get the accent right. Not only does it teach the language but it is also full of interesting tidbits of information about Catalan culture. The topics in the dialog seem very modern and relevant so it is great training to try and join in a conversation with a group of modern Catalans.
Another review mentions that the vocabulary it teaches is a bit limited. I don't think this is a major problem because you will want to use the course alongside other types of resources anyway and these are often better ways to learn words. If you have a dictionary handy you can find the meanings easily. I am learning new vocabulary by speaking with friends, reading articles and watching TV3 online. It is easy to make the words stick in the mind with something like AnkiDroid and spaced repetition.
One minor complaint is that I find that in real conversations Catalans tend to mix in a few Castilian words and expressions as well. The book so far hasn't mentioned this, perhaps because it wants to teach pure Catalan, but I think it is quite important if you really want to speak the 'colloquial' language. My advice is that if you come across a strange word in the wild that you can't find in the dictionary, don't be shy to also check for it in a Spanish dictionary!