I hope you have a big memory card
I'm really enjoying Killzone: Mercenary -- when I can find the space to fit it on my Vita. I obtained the game digitally, only to find out that there was a massive 1.1 GB launch patch, and even with a 32 GB memory card my capacity was hurting.
Now, Sony has announced that another 1 GB patch is live, and it needs 2GB to install. The patch is aimed at fixing connectivity issues, and making multiplayer a more overall smooth experience. The good news is that once it is applied, the old patch goes away. But still, I feel bad for anyone with a smaller memory card, and those 64 GB cards can't come soon enough.
Killzone [PlayStation Blog]