I keep my vita to play the assortment of ps plus games they put on the service each month. At this point I have a pretty good backlog of indie games I should be playing on my vita too. Also like the PSP before it the vita also looks like it'll be a haven for Japanese RPG's and visual novels.
@johaneriksson The way ps plus works is that if you download a game during the period it's on plus then you keep it till your subscription stops. Once you stop subscribing all of the games you got via plus will not work anymore. Also you would have had access to more games if you subed 4 months ago since they keep rotating out games every month.