Like Bartre, I do wait a couple years. Infact, the only system I can recall buying on launch, was the GBA.
It's nice to have the shiny new gfx. There are still games that come along that interest me, even if they're fewer & farther between with each generation. I'm excited about another InFamous game for PS4, I was sadly guessing they were going to end it with IF2. I also heard recently from a great source, that Naughty Dog is working on a new Uncharted, so I'll assume it's for PS4(though, I'd prefer a new Jak & Daxter, & I voiced my opinion to that source). I don't care about sharing/Facebook/etc., but it might come in handy to record my games, if only to replay some spot of a game that I really enjoyed.
I've read that it IS backwards compatible with PS1-3. However, there was some question as to whether it can actually play the real discs, or not. Sounds like somehow, the cloud thing is involved in the b/c. Got this from magicbox:
"PS4 will use Gaikai's cloud streaming service to provide backward compatibility for PS3, PS2, PS1 and PS Mobile games on PS4."
As for the Vita, Ys Celceta comes out in September, so, that's my reason for getting a Vita, though I'm hoping a new model &/or price drop will happen beforehand. I might even pick up Ys, & then wait for the price drop. There was a new model that they registered the copyright for, with an HDMI out & some other things, hopefully that is coming soon.