No idea if this has been hyped all to hell or not, but being a 2 part 48 page comic is great for people like me, who have stopped collecting single books (Honestly, it comes down to weight. I decided I wasn't going to move more than one box the last time we moved, and sold/gave most of my collection away to a friend.) One of the few comics I did keep is the last time Gaiman wrote Batman (With a really cute cameo by John Constantine) so, I will likely ask my brother to go pick this up for me. Not sure if this plays off of the Morrison stuff or not, but it looks fun.
You're right, that's the worst part. The material is right there, there's a ton of great stories you can tell based on Cap's death. And Loeb is a good writer, much better than this mini would indicate. But it's not coming together here at all.