I signed up for PS+ today mostly to get some of those free games. I planned on getting Gravity Rush (for my Vita) at some point, and this saves me the money... as long as I'm a PS+ subscriber.
To add, Sony is having a 12 months with 3 extra deal where if you subscribe for 12 months, you get three extra. Apparently, this also works with the cards, which means any cheap, eBay cards will also work and provide the games that I mentioned above ( there are more than just Gravity Rush ). You can see what games are available through Sony's new online store: