The PSPgo was an experiment, in a way. Sony seemed to be trying out some things, like removing the UMD drive and adding onboard memory. The form factor was considerably different from previous models, though the innards were comparable. Sadly the PSPgo flopped (though it has loyal fans)--if it had succeeded, I expect the PS Vita would be quite different from the promo photos we've seen so far. If the PSPgo had done well, I'm pretty sure the PS Vita would have had a similar form factor, but much better specs.