The people who loved Dick as Batman are all for it, the people who didn't are all against it. :)
In reality, there is a bigger part of me that is FOR it than against it. Probably a 60/40 split, in truth. I cherish the Nolan films and don't want anything to really besmirch that continuity and trilogy. But like I've said, the last 10 minutes of Dark Knight Rises is so rewarding, fulfilling, and invigorates the imagination that I wouldn't mind seeing something along these lines.
Warners is trying to make it so there are three instantly recognizable faces in the JL movie, and then only have to worry about introducing three more. If I were DC/Warners, I would do a few 10/15 minute "featurettes" that introduce us to Wonder Woman, Aquaman, Flash, and any potential hero that would be in the film. Throw then in front of various other WB movies. Get a feel for what works, establish minor plot points, and cast Scott Speedman or Daniel Lissing as The Flash or a recast Hal Jordan.