Since the Dungeon Master's Guide 2 has been released for the 4th edition, there's been nothing but praise for the book as a great contributor to the game itself. From the reviews, it seems to be choked full of advice instead the crunchy add-ons that the Player's Handbook 2 and Monster Manual 2 have been.
It also addresses earlier issues that DMs may find hard to handle such as skill challenges by dedicating a whole chapter on it. The book also has a chapter for paragon campaigns which is just about the where most groups would likely be if they have been playing since the launch of 4E. It looks as though the DMG 2 is really filling up the gaps that were left in DMG 1.
I'm really interested to read the DMG 2 for myself and I have to say that I impressed to see what the designers have decided to put into this book. Even if you are not planning to get PHB 2 or MM 2 for the crunch fest that they are, I would believe that DMG 2 is a great successor to its predecessor.
If you can't take my word for it, then read the reviews of it by bloggers from the RPG Bloggers Network. Add these voices in and see if you hear an echo.
Review: "Dungeon Master's Guide 2"
Dungeon Master's Guide 2: Skill Challenges
What's cool about the DMG2?
DMG 2 Lessons
The RPG Athenaeum
Product Review: D&D Fourth Edition Dungeon Master's Guide 2