Don't know about limited numbers but we got a room rate of $155 for PBH last month. You don't need to have the entertainment card in your hand to book the rate, but you do need it at time of check in. There are some great savings on restaurants as well
Many of the coupons in the book are similar to the vast amount of coupons you find in and around Orlando. But what it does is give you time to look at the book and choose where to go if you want to and find it on a map.
Last trip we collected a bag load of coupon books while in Orlando but did not really use any as could not be bothered to find many of the places.
You also get good rates for car hire and many hotel groups.
I am not saying you can't find it cheaper on the net for some things but you do get some good discounts.