So I had about 15 minutes play-time yesterday and played through 4 different tracks.
Sony staff were super strict about photography so I'll just describe my experience in words!
The vita feels nice. The analogue sticks are a little sensitive/delicate but they have a nice rubber coating and I was able to race intensively with no problems at all. The screen appears to be about twice the psp's size but it's not of course - the extra details afforded by its much higher resolution certainly help.
The framerate seems solid and smooth but when there was a lot of action on screen the distant foreground resolution drops. It's a new kind of sacrifice but considering what you're getting in exchange it's probably worth it.
Couple of niggles:
Ships still bottom out even if you pull the nose up on jumps.
The missiles look like they're from HD which doesn't match the timeline for 2048 (they have that red twirly particle effect)
Barrel rolls
Sadly I couldn't hear the music or sound effects clearly because of background noise at Gamescom.
Level design is awesome. Ships look great. The game really feels like it is set at an early time period - just with more detail than we've seen in most other wipeout games. The scenery is incredibly dense with some nice layering effects when transparent tracks twist and swoop under themselves slightly (this is most visible in a track called Sol). This means you can anticipate a dip in the track unlike a solid track where you would have to reach the dip to see what's next.
The touchscreen stuff actually works much better in practice than I anticipated. You can very quickly choose your game mode by jabbing at the icons on the screen like an iPhone. The touchscreen was very fast and responsive.
It feels like a new wipeout. Yes, some features have carried over from the last few iterations but the level design really feels fresh. It doesn't have the "rehash" feeling of many of the last few recycled tracks in pulse, pure and HD. I think the tracks are what makes this game shine.
I'm very tempted to import a Japanese PS Vita but I'm concerned about the location based limitations an language/region locks etc.
I had a decent session and got a good feel and a taste for the game. Sadly this means I'll be craving 2048 for the next while with no relief!!