1. Mspress books did help me in getting certified for 2005 & 2008, and I'm going to wait for the 2012 kits too. I'm an experienced DBA but I find that the kits guide me on what I need to focus on, as I tend to get carried away when I use books online. Of course, I do cover the book very quickly since I already know most of the topics, but rigorously practice on new features, like AlwaysOn in 2012. Some people simply find the exams outlines sufficient enough. If you're very experienced with the product, then you should be fine.
2. The exam vouchers enable you get some sort of discount or offers. You have to wait to see what types are offered. The 2005 one, for example, offered me a chance to retake the exam and also a 20% of the actual price of exam itself.