I have the PHBII as well: here are my thoughts on it:
Astonishingly high Crunch to fluff ratio. Every page in this book leads to something which, if considered, can be used either in a regular gaming session, or in carefully crafting your next PC.
The new classes (There are four) all have powerful, distinctive flavor to them which sets them apart from other variant core classes. Most intriguing out of these four is the Knight, who exists as an upstanding one-on-one fighter who specializes on calling out individual enemies and taking them down. The Knight's special powers are bardlike in nature, granting simple stat boosts as long as the Knight adheres to his own code. in the event that he violates that code, he merely looses one use of his powers, no repenting, no special magical item necessary to keep him on that straight and narrow.
Moving on to the next sector, the Expanded classes treats Players of a wide variety of classes to new options in character development. Reguardless of what class you enjoy playing, there is an option here for you. Rogues, bards, wizards and warlocks. Nearly every class in the book comes with a single line option for your consideration.
The new feats are both numerous, and omni-functional. Many of them have fairly high prerequisites (base attack bonuses of +10 or more in some cases) but all of them are actually useful given the correct circumstances. Another victory.
There are so many new spells, I can't possibly provide more than a brief overview. Spells like Whelm (which does 1d6 + 1d6/2 levels in nonleital damage) can allow even the starting party wizard to have the power to bring 'em back alive. and the 2nd level paladin spell "Mark of doom" will keep nere'do wells in line once you've caught them. Plus, the new "polymorph subschool" is astonishingly well defined, and can go miles towards protecting the players from polymorph abuse.
Chapter five is all aobut backgrounds and building a character that is well rounded and believable. finally! a how-to to writing the backstory! Never again will i have to hear about how a character's mother died during childbirth, then died when she was eaten by a troll, then died by taking her own life. For some reason, I foresee a lot of "Vengeful rebel guttersnipes" in play though...
Chapter six is about group interaction. While it presents an idealized view of character to character planning and strategy, it is also pretty good advice. AND it includes a section on Teamwork bonuses, including what the leader needs to have in order to pull it off. For instance: to pull off a Massed Charge (Where everyone charges on the same initiative count, all attacking the same target) one character must have at least 5 ranks in balance, and all others need one rank. Looking through this section for special tricks you and your party can pull off is a must.
Chapter seven is all about finding your place in the game world. Otherwise known as "If my rogue has to join the 'thieve's guild', I will smack someone." This chapter is not just about randomly doing favors for whoever is in charge, it's all about actual social and racial affiliations! This finally helps answer the question: What is my dwarf's standing among other dwarves?
CHapter eight is perhaps the one to cause the most controversy, as it is about changing the way you created a character. If you've allways regreted taking those item creation feats in a fast-paced no-time-for-rest campaign, this chapter is dedicated to you. You can change everything from your clerics domains to your fighter's ability scores, through proper training, most of which can be done on the side.
Overal, i strongly reccomed buying this book. Utterly full of things, NPC's and ideas for any campaign.