oh, it's worth it!
I just finished Spells and Spellcraft a few days ago, and it's not nearly as bad as you make it out to be, Limper. In fact, a good portion of it is quality stuff, although i do have some gripes. One of my biggest gripes is that in a lot of places, the rules tend to deviate from typical 3e mechanics, espically things like alchemical item creation and construct making. They're not incompatible or anything, just not quite as streamlined as they could be. still, it's a minor issue. TypeO's are also something of an annoyance. damnit guys, stop watching those invader zims and get back to proofreading!

Also, If you're a big chaos magic fan and want to develop this concept thoroughly in your game, you should probably look somewhere else. 'Course, if you just want to dabble in it, then the rules they provide are pretty much all you'd really need.
In fact, that seems to be both the main asset and main problem with this book: It has a decent-but-not-heavily-detailed amount of information about a very wide variety of topics. You want an elemental/undead/parasite/planar/etc.... familiar ? it's in here. Just don't expect more than two or three of each. (which is OK with me, after all, how many times are you going to
need those undead familiar stats ?
There's a bunch of interesting new concepts/new takes on old ones, and enough rules for each one to get playing with a minimum of hassle. Some of it may just need some tweaking for it to make sense. (why should all wards be 30' in radius?)
The art's pretty good, but sparse. My favorite pic is the concerned looking frog sitting on it's assed-out master's chest, next to the arrow. Also, I don't know why all the bows in the book are strung backwards, must be a personal thing :-}
The book qualifies as "extra-crunchy" leaving out annoying bits like 'wizards and the world in which they live' crap that plagues wotc spaltbooks with large amounts of the obvious. if you buy books by density of useable information, then this one is a good value for the buck.
Well, that about ends my random impressions/reviews on Spells and Spellcraft. I was going to do a summary of all the new stuff the book had, but it started taking a really long time, which i suppose speaks well of the book. In fact, i'm happier i got this book, covering a nice, wide variety of topics that i would have been if i'd dumped my 25 bucks into a book dedicated entirely to wild magic, or golems, or arcane libraries, or alchemy...etc. It really does expand nicely on a lot of magic-related subjects.