I was previously borrowing another players copy of the original DM screen but picked this up when I saw the revised info. They've done a good job of putting in things you might want at the table too often to look up easily. Skill difficulty by level is great for winging skill checks, and there's a great table of conditions which is handy.
For example, when I dropped my players from a few hundred feet ont a rural villiage, the warlock wanted to know if teleports obeyed newtons first law. That last sentence possibly made me the nerdiest guy on the planet but PRESSING ON, I decided that when your teleporting with magic Mr Newton has definately left the building, but it would take a little extra magical shenanigans to override the laws of physics; one "Hard" DC arcana check later and the warlock had made an impressive entance believing I had prepared a skill challenge for the whole thing. Then he was kidnapped by Asmodeus but that's another story.
Anyway back to the topic at hand, I'd recommend getting this for any newish DM out there, or any expert who doesn't like to look things up if they can make them up. My friendly local gaming store (in the UK) has had problms getting hold of these from their supplier too so Amazon seems like a good place to get it.