Beth,
I dont have any Nader Shagagi DVDs, but I have heard good things about them. They also sound a lot like traditional yoga instruction in a typical class in India. The format sounds very similar to a live class with my yoga teacher in India.
In many scools of traditional yoga here, Vinyasa (flowing from one pose to the next) is not used until the students become proficient at the poses. It is easy to not do the pose correctly when in flow mode, or not have time to perfect the pose (everything from weight distribution, to positioning of limbs, angles of the body can make such a huge difference).
Sun Salutations followed by static poses is a great way to improve on form and complements power yoga DVDs (you will find you are better able to achieve a pose and more aware of alignment even when flowing).
I am not sure of Nader's personality as an instructor as I have not used his DVDs.
~* Vrinda *~