I just got mine in the mail two days ago. Wow. I can't believe how big that thing is! I was surprised, and even more surprised that it is hardbacked.
For those people who like to flip through and daydream about which new armies they would love to make, the guide is fantastic. For those people who are constantly searching for the right bit for their conversion, the guide is fantastic.
The tactical information inside is ok, with good advice, but not complete for any army. The painting stuff is decent, though I've seen most of the advice in other formats (the GW website, White Dwarf, and codexes). I've even seen a lot of the featured models before. So this is less exciting to me.
But if you are new to the game, or don't get white dwarf, then you may find LOTS of great things inside.
I felt that my money was well spent. I'll be pouring over that catalog for MONTHS to come. I've got lots of conversion ideas floating around in my head, and this will help me find every part that I need.