I took the new Prius for a test drive today. I've owned a Prius since 2001, and have found most of the marketing slogans to be true. (I get an average of 42 MPG for combined town/country driving, not some theoretical upper limit.)
The new prius has been drastically redesigned; the engine is more powerful and the body shell is different. It uses the same 1.5 petrol engine inside, but the new hybrid drive train -- sorry, Hybrid Synergy Drive -- has been updated extensively.
I don't think much to the new design of the body; it looks more like a corolla than the original prius. The vision is also hampered by a bar across the back of the rear window; whilst the salespeople say that it's something you get used to, I'd prefer not to have to get used to it at all.
The new drive train is excellent, and re-generates much more electricity than my original prius does. It's certainly likely to be why the new prius has a much better quoted efficiency than the original.
But personally, I'll be sticking with my old prius. You can get a set of clubs in the boot and four full height adults in the car. I found sitting in the back of the new prius difficult, as I am 6'2" tall; the brochure claims that it can fit four 6' adults in it (so doesn't help if you have tall friends).
Lastly, the marketing department has changed Latin -- Prius used to mean 'Going forward' a few years ago, now it means 'Ahead of time' :-)