It's unlikely I'm going to buy the 4th book of a series of which I didn't buy the previous ones, but at some point a couple of months ago I thought CAdv might have had something really interesting. However, I had the same feeling for CWar before I read it, and the same with CDiv, and the same with CArc...
10. Put Those Skill Ranks to Good Use
I think S&S did a very bad job about skills, so I was expecting CAdv to take the chance of expanding skills use a lot. The potential to do so is there, does it look like the book gives a new edge to skills? I can't say from the preview, but I seriously wish it isn't just about doing things faster... This section is the only hope left for me to get this book.
I like feats, and the Complete books have plenty of them, tho many are just reprints. This one isn't a new idea tho. There's Sculpt Spell (unless it hasn't been reprinted yet, and this new feat is Sculpt Spell renamed) which is already one of the cheapest metamagic around. If it's a new one, ESA is probably a nonmetamagic lesser version.
8. Expanded Multiclassing Options
As someone mentions, how can one "overlook" a multiclass option which is simply not possible? Yes, you could be an ex-Bar/Pal or ex-Pal/Bar, but shunning such difficult path is NOT "overlooking"!
In any case, good idea to make a new character concept/combination available (which we should remember however that it wasn't available because of questionable alignment restrictions). Not-so-good idea to make it available through a feat, but that already has a sort-of precedent with Practiced Spellcaster. Probably we wouldn't need specific "fixes" to each multiclass combo if they had thought of a single fix for multiclassing in general.
Not many "new" PrCls in the list really. Another shaping character... another bounty hunter / vengeance character... another assassin? There's so many PrCl around to cover the same few concepts... in a way it's positive to have different options for the same thing, but in another way it waters down the role of classes in a class-based game, IMO.
6. Tools of the Trade
5. Alchemical Wonders
4. Go Exotic
3. A Grab Bag of Magic
New tools and materials? Well, why not? These can always be nice additions of course.
As usual, there'll be new ones but also about half will be just reprints.
The ninja could be ok, but I still think the idea of spreading oriental classes in many books is not elegant, and it doesn't care for those who really play oriental adventures.
The scout doesn't sound like a scout if he doesnt... scout! Sounds like the 3.0 Ranger instead.
The spellthief is a (not new) nice idea, but IMHO it shouldn't be a core class. It might be a core class in a special setting, where magic works in a way that there are people who cast spells and people who steal them. But it's a too much specific niche that is just perfect for a PrCl.