We did this in May because we had a refund that would have taken a long time to process if we had not added it to our package (we had changed our hotel...) and I thought it would be good to just have that expense out of the way, but we won't do it again.
We got a mixture of Character Breakfast (good), specifically Goofy's Kitchen for dinner (did not want that, but no face value on the voucher, so too bad so sad or lose the cash), snack (with a face value of $6.56 or thereabouts), breakfast in the park (with a face value of about $10.59), $10, $15, and $20 vouchers (I think the kid's ones come with $5 instead of the $20).
It is not convenient (or it was not for us), because for almost everything except a corn dog and a drink, we had to add money to get what we wanted or order something extra that we really did not need so we would not lose the change. We actually ended up ordering more than we would have normally because we had the vouchers - ie. at Cafe Orleans we each ordered the pommes frites (very good - but WAY too big for one person and we wasted more than half each) and a Monte Cristo each (again very good - but WAY to rich to eat a whole one). We would have ordered one each to share if we did not have the vouchers and would not have wasted both food and money that way.
We still have several vouchers left over as well that need to be used before January 2009 - but that's okay because we are going back in October and will use them up then. But we will definitely not buy the plan again.