What do you get right away? Well each category you vote in will score you a free downloadable theme for your system. I'm guessing they are more or less ad type themes for the games in the category but hey it is at least something nice for just signing in and tell Sony what you think.
As for the thing you will get later on, well that is a discount for the games that win the award in the categories. Nice right? Well it could be, as suggested by some of the commenters on the blog, a way to get games you don't have yet at a discount. I would hope, and I will, people would vote for the truly good games so that they get spread out further and those developers can have a chance to make more games just as good.
It is probably a bit farfetched that people are going to try and run a ballot stuffing campaign to get the games they want at a discount, but I am sure it will sway some people to go that way a little bit. Maybe this was something that Sony should have kept to themselves for now to try and keep things a little more biased with the votes.
As always, we'll see. Until then go vote and enjoy those free themes for now.
Source: PS Blog