I tried Pimsleur's Method for German language- found it quite useful. Didn't try any other Pimsleur's course, though.

Isn't standard Mandarin from around the BJ area? That's what they chose then. So be it. I quite like that proper Mandarin rathern the 吃 = ci that you often hear in other parts.

To the Pimsleur, it's very good ADDITIONAL to whatever course you are doing. Even with I, II & III you will still be beginners level. Due to the nature of the method you will lack examples and deeper knowledge. As example, they don't go deep into the numbers. I strongly don't recommend as ONLY course. 

PS: I did all 3

It's okay. They use a Beijing accent though which may be a bit of a turnoff if you want to speak standard Mandarin. I mean, it's not that different but if you're not actually learning the language in Beijing it may sound a bit weird once you get to China. It's like learning a Manchester accent and then finding it weird English people don't all sound like that. :P