Howdy Steve -- I know this all feels like 'gambling'
I really do not know how many vouchers have been given out. According to the program manager, they *think* that if you take it within the first 10-14 days, you are probably safe. But that is not a guarantee! So, if you're willing to take a little risk, you might wait until, say, the 18th, knowing that there is still a chance that you won't get in.
It is just so hard to tell -- this beta exam *has* generated more interest than we expected. But, I suspect that a lot of people with vouchers will simply not feel ready, and not show up.
good luck either way...
-Kathy