Any good?
Fizz
Much better than Number IV. Many of the monsters are excellent. Only a couple are average. Even when they cover hobgoblins, kuo-toa and mind flayers they give you enough new material that it isn't simply rehashing old stuff. I have a bit of a problem with a few of the CR's but they could easily be changed. All in all, I was very pleased with my purchase (even the art was better than normal).
Phil's description is more or less a good one. If you have the spare cash to pick it up (or can buy it used), I would definitely invest in it. I own it and have used it and I like it.
One of my players has said its very good although I have yet to see it.
It appears wizards had an even/odd rule. MMs 1,3,and 5 are awesome, while 2 and 4 are pretty bad. Doesn't bode well for fourth edition.