We've poked around the app for a few minutes, and it does feel peppy compared to what we experienced with Facebook (while it was available, anyway) -- the only oddity that's arisen lies with the map functionality, which opens a Google Maps page within the Vita's browser rather than its Maps app.
Another Google-dodging feature in the new browser: Highlighting a street address on a Web page launches a map, with the default set to Microsoft's Live Maps (though you can change this default to Google Maps).