Yes, you should. Especially since you have PS+, you already get about $100 worth of games for free... more if you don't have a PSP.
For me, it was a great buy since I never owned a PSP, so I have lots of shit to play. Granted, I spend more time with PSP and PS1 titles on it than actual Vita titles, but some of the cross-buy stuff is killer, and the Vita is a sexy system. I just hope it starts taking off soon...