Firstly, the big question: How did it look? The answer: As good as can be expected.
The graphics of both titles are generally excellent when compared with other HD collections. The details now present on the character models are crisp and clear (as many were taken from Dream Drop Distance), as are the background textures. The only graphical blemishes are the pixelated diagonal lines that sometimes appear where two textures meet.
As for gameplay, there were two different demo stations set up at the Square Enix booth for 1.5 HD ReMIX—one for the HD version of Final Mix and the other the HD version of Re:Chain of Memories. Each of these demos had three different playable areas from across each respective game's story.
For Final Mix HD, I spent time gathering items for a raft on the Destiny Islands, fighting my first boss with Donald and Goofy in Traverse Town, and facing off against Captain Hook alongside Peter Pan.
The most obvious change from the original version of the game—other than the graphics, of course—was the addition of the triangle "special action" button that didn't first appear in the series until Kingdom Hearts II. Originally, special actions were a cumbersome part of the battle menu, so this is a welcome change. Other than that, the controls in Final Mix HD were identical to those in the original version—which is to say, pretty bad by today's standards. Sora can only move in eight directions (instead of the full 360 degrees of later games) and the camera might as well be the final boss of the game for all the aggravation it causes you. There are also a ton of collision errors with Sora ignoring ledges he should grab on to and other similar issues.
Chain of Memories HD, on the other hand, looked as good as Final Mix HD but had none of the antiquated control issues. For Chain of Memories HD I spent my entire play time as Riku—though Sora was playable in the two other levels present in the demo. He controlled perfectly—most likely due to Re:Chain of Memories being built on the Kingdom Hearts II version of the engine unlike Final Mix. The loading times when creating each room were a bit worrisome, but none lasted more than ten seconds.
In the end, after my short time with Kingdom Hearts 1.5 HD ReMIX, I am quite excited to spend more time with this collection. It is a great port and any flaws present in it were there in the original. It's an impressive feat, especially when you consider it's all the work of two lone individuals.
Kingdom Hearts 1.5 HD ReMIX will be released in Japan on March 13, 2013. There is no word yet on an international release.