The Lurk is just lovely. The increasing options for sneak attacks, make it usefull in all the situations that kill the straight thief. They are already introduced to my campaign world, which has a strong psionic presence.
The Ardent is a good concept but I have tried a few trial characters & NPCs and haven't gotten it to work well. To create a useful character you have to cherry pick domains that work well togeather, and if you do that it reduces the pure ideology of the class that makes it so interesting.
I still like the changes to Astral constructs, weaking them and adding flavor - its all good.
before this I had excluded them from my games, they will now begin to show up.
the feats are lacking, the XPH feats are better in most instances, even feats from Dragon Mag. are generally better than found in this book. The repition of slightly different concepts, just fills space. The racial feats are generally poor, while the flayer heritage raises to many biology questions to be sataifying in use.
The powers vary - Dampen power is a new fav of mine, Primal Fear (a swift doom, useable on multiple targets - nice. The reprinted inconsistant location, and lots of swift powers look fun. The stygian line of powers looks just aweful. while many others are not worth taking.
Llike Korimyr I find the page count insulting. I would even prefer more reprinted material so I don't have to go hunt it down. As the primary/only support for Psions, its not enough.
The book is worth it to me for the Lurk and the revised Astral Construct & clarified rules
(power stones, DC scaling, etc) but its hardly a good investment on a cash vs use ratio.