Check this out (PlayStation Blog).
Starting tomorrow, I'll be able to pick up Mortal Kombat on Vita for five bucks with my Plus discount, and so am very pleased I reigned myself in over the past year and waited for its price to come down. Prince of Persia: The Forgotten Sands is... arguably worth four bucks. I wouldn't hold it against you for buying it, but keep in mind, it's not one of the better ones.
Scott Pilgrim Vs. The World: The Game is definitely worth two bucks, and you know Shadow of the Colossus and Batman: Arkham Asylum are worth five.
One week later, some new sales will go live and I'll have to stop myself from checking out Silent Hill: Book of Memories for $7.50 and LEGO Batman 2 for $5. I strongly advise against paying money for The Force Unleashed II, but Alice: Madness Returns for four bucks..?
I've already got two copies of that game on Bluray, but yeah... Yeah, I'm gonna' have to do that - and you should too.
[update] And we just got this month's PS+ ICG update:
Battlefield 3! Commenters on the PS Blog have been begging for that one for weeks - and while nothing else there really appeals to me (I've already got Jet Set, I never became an Oddworld fan and Dokuro was pretty boring), I'll be interested to check out Metal Slug. [/update]