The Vita is a pretty good system in terms of hardware. It's biggest drawbacks are:
1-Lack of games. (Though if you have PS Plus then the instant game collection does add a few titles to your system... Disgaea 3: Absence of Detention, Uncharted: Golden Abyss, Gravity Rush, etc...)
2- Sony's stupidly overpriced proprietary memory cards. (100$ for a 32GB card. Anything less than 32GB just isn't worth it since you'll burn through space in a hurry if you download games or put HD movies or high quality audio on the memory card.)
3- Sony's decision to have the Vita/memory card lock itself to one PSN account. (So no sharing Vita with siblings or spouse like you could with the PS3.)
Though it makes sense why Sony would offer their own PSN card or Sony Store points... It offers an incentive for people to get Sony Content (which is easier and cheaper for them to distribute. Since they can simply send you a message on PSN to give you the 20$ PSN voucher. And plus this way they don't have to pay Amazon or another company for the gift cards and watch people use them to buy 3DS games... which would be a bad business move.)
Besides, if you knew someone who was already looking to get a Vita this'd just be a way to get yourself a bonus.
I can't imagine it actually boosted sales that much, but it certainly couldn't hurt. And it would help get some more exposure for the Vita. (Though a price cut would certainly get sales up... When they cut price in Japan, the Vita exploded in sales... According to
one source, going from 11,000 to 62,000 units sold in a week. So if that's what happened in Japan, I'd imagine something similar would happen here in North America.)