It is indeed out, should be out just about everywhere today, yesterday it was mostly at places like EB and Gamestop. Definitely an improvement over the original and with a wider variety of things to do. I've noticed that the ball rolls along much better, although it's hard to describe exactly how. The ball definitely reacts better to oddly-shaped pieces which affect how it rolls. Also the graphics are slightly better with a very noticeably improved framerate. It's also "busier" than the first game, it seems like there is more stuff moving around and definitely more objects total to pick up, you get big fast on some levels, and by KD1 standards you think you are doing fantastically only to realize you didnt pick up half the things you could have. Again, the goals in the game are very "modest" just like the first one, so I havent had much problem unlocking the levels, although the game hangs up your progress slightly by (I believe) requiring you to find all of the cousins at couple of points before you can unlock the final few bonus levels.
The size and scope of the levels are pretty amazing if you're used to the levels in KD1.
Spoilers ahead...
There is another similarity to KD1 in that there is a main "world" level which you have to play at varying points in the game where the king will give you more time and a bigger size to reach each time in this same level, sometimes starting you out further into the level. The other levels, of which there are many, are like bonus areas for specific tasks which are not part of this main level - off the top of my head I can think of a zoo level, a racetrack, a campground, a solar system, a school, a ski resort, you've probably seen a lot of these already. But the "main" world is something else. You start off in a house and then when large enough you can go to the next area, the game actually has to load the area in this time because it's ENORMOUS. The town is just god-awfully huge with so much going on that it's not like anything in KD1, and as near as I can tell you could keep going until you've rolled up most of the world as it just never seems to end! I couldnt even get to a point where it loaded in the next level. Hopefully later in the game (although I fear I'm very close to the end) it will give you enough time to completely explore the world, it just seems to be never-ending.
Here's what I found in a faq on gamefaq's that better describes the progression I'm talking about:
MAP 1 - The inside of a house, with tables, sofa, and chairs.
[ Leave by rolling off the balcony. Caution: once you leave this area, you
can never come back. ]
MAP 2 - The garden of the house.
MAP 3 - The garden of the house, plus the town the house is in, and the
playground of a nearby school.
MAP 4 - The garden, town, and playground, plus two extra urban areas.
MAP 5 - The garden, town, playground, extra urban areas, plus two themed
areas meant to represent France and London, and also a construction site.
MAP 6 - The garden, town, playground, extra urban areas, France, London, the
site, plus areas meant to represent America, China and India.
MAP 7 - Everything in the previous map plus areas to represent Egypt,
Russia, a giant robot launch site, a rocket launch pad, etc.
MAP 8 - Everything. In the world. And Atlantis. And the King walking
around. Enjoy.
These different "maps" are actually one huge, huge, huge, huge map. For instance going from map 1 to map 2, then 2 to 3 you have to go through cones just like in the first game. The difference is that once you are large enough to get through the cones the King notifies you like in the first game but then loads the next portion in, you can still roll around where you are and traverse back to earlier sections (except the house, you'll see why) or you can move on to the new section by rolling over the cones. The scope of these areas is immense, it makes the final level in KD1 look totally puny.
So far it's only given me enough time to go from map 1 to map 3, although one level started me out in map 3 and I was able to get through most of map 4. I'm hoping at the end of the game it gives you a chance to go from map 1 to map 8! If someone's already done this let's hear about it please.