I believe they put out 600 vouchers. Once the 400th beta-tester has "uploaded" the voucher at a Prometric site, further vouchers for the exam will be rejected. At least that's what I have come to understand. In other words, you cannot know whether you will be able to take the
test based on the fact that you got a voucher. On the other hand, many of those 600 will never register for the test or just won't show up. I'm taking my shot at it tomorrow morning with unadequate preparation (due to some busy times at the office) just to be sure...