I've only glanced through the PHBII. My group tends towards low to mid level play (say, the sweet spot between 3rd-10th level), so maybe I'm missing out on the benefits the PHBII would bring to higher level games. I read through the classes, and while I thought knight was fairly well written, none of the other classes made enough of an impression on me that I can even remember them. (Except maybe, Spirit Shaman? A fellow player has one of these now, I'm assuming it comes from the PHBII. It looks okay in play, but I haven't seen anything that made me think it was better/worse/replacing/all that different than a cleric or druid.)
AE, however, I really like. The classes, the races, the magic system; there's a lot of good stuff in there. As a GM, I've run AE/D&D games that left all race/class/magic combos open, and I've never found a problem with it. Because of certain rules tweaks (mainly in skills), I decided to run it as an AE game with the D&D material supplemental to that, in a homebrew setting. But for me, AE and D&D are chocolate and peanut butter. Unfettered/rogues, barbarian/bear totems; I'm all about it.