I justified it with my PS+ subscription earlier this year. I think I've got like 11 games for free through it, and that's just on the Vita. The quality obviously varies... but free is free! In my case I really wanted to play Uncharted: Golden Abyss and Virtue's Last Reward.
Also remember that there's a couple of decent games available for free through the PS Store - Frobisher Says and Jetpack Joyride.