My wife and I got it nearly as soon as it came out. There's a LOT to say about it, and I don't have anywhere near enough though process to name it all but I'll point out the good stuff.

First impressions::

-sound and interface-
It didn't take long to tell that all the previous ideas for DDR had been scrapped in this version. From the pure white with red trim case to the new deep-space sounds that replace the old hip-hop scratches. This DDR is meant to feel different, and does. It has a distinct spacey feel that I'm sure was Konami's intention.

-gameplay modes-
Looking at the modes of gameplay I was instantly curious what this new "Stellar Master" mode was. Upon further inspection I found that they had twisted and construed Dance Master mode straight to hell (ahem, but in a good way). They took the idea of challenges and went a step further.

-starting freeplay music lineup-
The music you start with is pretty impressive. Not that many songs but the songs that are there are pretty cool. Ranging from current pop and pop-rock to classic Bemani music. At first it does not seem like Konami would ever live up to it's boasts of this DDR having the "most music EVER..."


After a few hours::

-sound and interface-
The interface holds up pretty well with it's overhaul. It has sort of the same wireframe look that Extreme 2 had, only more curves. When selecting songs you can choose from easy songs, medium songs, hard songs, or all songs, aside from the normal song difficulties. Song difficulties have been renamed to Beginner, Basic, Difficult, Expert, and Challenge, if I remember correctly, which is not that hard to get used to, but seems a bit pointless. Instead of AA*, AAA*, etc, you have E through A, and A "PiX", meaning nabbing an A can be a bit harder, and is somewhat impressive in this version. "PiX" consists of only Perfect and Good, as far as I can tell, so getting a perfect combo is the only way.

-gameplay modes-
Free play mode is a hybrid between Extreme 2 and all other Arcade style 3-at-a-time setups. You play your songs 3-by-3, but failing or finishing your 3 will not send you to the menu screen, but rather back to the music select screen with a new set of 3 waiting for you. There are courses and workout modes that are basically the same as you're used to in Extreme 2. Stellar Master is a very pleasing way to earn your points (which you earn in free play mode as well, of course) so you can unlock music. You enter a "Stellar Joint" and finish off challenges. For example, get an A or better on 3 songs of Beginner, Basic, or Difficult, or select 3 songs using Random, and finish them. These challenges are open ended and varying, but can be extremely difficult (3 songs, speed x5, ghost arrow, expert or challenge o.O). Once you have cleared a percentage of goals, you get to challenge the first Showdown. There are 3 showdowns per Stellar Joint. Acquiring a VIP card (which you attain by completing the first showdown successfully) unlocks another Joint, with new goals. Each Joint has it's own set of music. This music is pre-chosen from the list of songs available within the whole game, some of which will be new to you. I'm not sure exactly how, but playing songs you don't have unlocked for free play mode will allow you to buy those songs. For example, play song A a certain number of times (I think) and you will be allowed to buy it from the shop (did I forget to mention the shop? basically the same as extreme 2). Play song A once, and it will appear in the shop as "Coming Soon..." A showdown consists of 3 to 5 (so far) challenged that you must complete. Sometimes it's simply a song you have to pass, or pass B or better, or pass A or better, or maybe alternate left and right arrows as fast as you possibly can for 20 seconds without letting the meter fall to 0. One was a long sequence of nothing but jumps. It's nearly like Konami borrowed a bit of inspiration from Warioware. True genius.

-music lineup-
This game has a lot of music. I mean a /damn/ lot. Some of the songs you'll see are familiar from older DDR and other Bemani games, some is somewhat familiar remixes, and yet others are all-new tracks just for Supernova. Songs range from Ska to Rock to Techno to House to Ethnic to Trance to Euro to Eurobeat... The list is huge, and I know for sure I have a ton more songs I have yet to lay my eyes upon.

Final assesment::

This DDR kicks all ass. I would suggest this DDR over every other on the market today. And no true DDR fan should be without this one. There is far too much music to play to, and far too much fun to be had in Stellar Master mode to leave this one out of your collection. Buy it. Buy it now.

So I managed to get my hands on a copy this weekend... here are my initial thoughts:

1. I LOVE the music in this one - much more varied, and a lot more fun.
2. The new "spacey" backgrounds are complete disorienting and distracting - damn them! :-)
3. I lost a couple rounds laughing at the characters dancing in the background - they obviously took inspiration from strippers for these!

Tons of fun - I highly recommend it...

I got this last week, and have been playing it for the past 7 or so days. I can't compare it to other games, since I haven't played those extensively (I have Extreme II and DDRMaxII) .. but I like how it has a cleaner/simpler interface. I don't quite like having to unlock songs via Stellar Master Mode - tasks, which aren't too difficult but are somewhat silly.

And thank you to the earlier reviewer, I've been playing each day .. going .. when am I going to get the "AA"s or "AAA"s thinking that I suck .. but now I find out that those don't exist any more! Argh!!!