I downloaded it the week of E3, when it came out.
My opinion - I was semi-anticipating Blue Dragon before the demo. It looked like a kinda fun, chilidish RPG.
What I decided after the demo is that Blue Dragon is quite possibly the Xbox 360 Masterpiece.
It combined (atleast IMO) the best things about Final Fantasy 6 and 7 together into one uber-game. It has FF6's great locations (Ruins reminded me of Phantom Forest), and the Fortress reminded me of an area right from Final Fantasy 4 (the Giant).
Gameplay wise, it reminded me of what made FF6/7 perfect - a very simple, easy to understand job system that just kicked butt. The dragon classes are amazingly simple, but have insanely good skills/abilities.
So the game went from a "probably buy" to "pre-order" status for me. Mind you, I've only reserved about 5 games my entire life of gaming (since 89) - only Final Fantasy 6, Super Mario RPG, Legend of Zelda: OoT and Oblivion have ever, ever, been games I've pre-ordered.
The demo had some real minor framerate issues, but otherwise ok. The voice acting in the fortress was rather interesting, in a good way.
The only thing iffy is the text - it's kinda small like Dead Rising, but not nearly as bad. I had a little trouble seeing comments on various skills, and item effects, but shouldn't be too bad.
Again, loved the demo. Some people thought it was only OK, but it's either because they don't like traditional JRPGs. This game IS a standard by-the-book JRPG, with nothing really re-defining the formula. However, it uses a perfected formula from what I've seen in the game. I know the full game is going to be fantastic.