Not sure what people are complaining about but this is a good next installment in this series of games. Instructions are given in the tutorial, as in all other games. Gear is explained in the tutorial plus seems pretty self-explanatory. If you want more info, just use the strategy guide. No need for a forum. I also enjoyed the subtle changes in obstacles and challenges. No complaints here.
Personally, I enjoy the game quite a bit. I like the idea of being able to play the game endlessly over and over. I get more bang for my buck that way. I have so many games on my computer that I've completed in a week and never go back to. I think all the "side" levels outside of the main story line is there so you have way more levels than just the 60 or so you would typically get. Meaning, I won't finish this game in a week and be looking for something else.
I do agree that it is annoying that it is so difficult to get 5 stars after the first few levels. Plus, I'm finding it near impossible to be able to upgrade all the shops as the items are too expensive. I'd like to be able to play all levels fully upgraded but I don't see how that will be possible. You also don't get enough diamonds.
All in all, I'm still going to finish the game and glad I bought it.