I registered on PS Australia's facebook page for a free 30 day trial, but then I caved before the email arrived (still hasn't) and bought 12 months access. I've kicked off a bunch of games downloading, though my measly ADSL1 connection means it will take about 3 evenings per game!
I'm immediately impressed with the value. The only game that I have downloaded that I actually wanted to buy was Gravity Rush (for PS Vita), which would have cost me $50 new, but I also grabbed Ratchet and Clank, Bioshock 2 and Little Big Planet 2 - all of which were semi interesting to me. I also grabbed almost every other free title to have as options, and then I got a dozen dynamic themes too.
I've got my eye on Sleeping Dogs, WipEout 2048 and Lumines over the next month.
I really feel it has added a lot of value to my Vita already, and has reinvigorated my PS3 too. Very happy with the purchase.