I got SC a year ago, and even as a DM, it's been one of my most-referenced books, mostly for the one or two signature spells I like to give a BBEG spellcaster. My players use it every single session.
For them, the PHB, SC, and PHB2 are the books that absolutely must be brought to the table. Even the stingy ones usually have a PHB and one of those two.
Actually, I think it has "most" of the expansion spells. Of course, every time WotC releases a new book with new spells that adds to the list (for example, the PHB II).
Thomas Percy said:
There are no spells from PHB, so it's not a complete book, it's just-another book.
If this had the PHB spells in it, then it would dive in my rankings. I already have a PHB (as do most people who would buy it), why would I want to pay more for those extra pages? I'm bringing my PHB to any game I'm playing, so it wouldn't be saving me anything .
I'm going to wait until I find it for around half the suggested retail price. There isn't any way I'm paying THAT MUCH for a book of spells, when most of the "useful" ones are already in sources that I own.
This book seems to be and ideal example of a useful book to have physically (not in PDF) lying at the gaming table. In fact, I"d almost think that, like the PHB, two+ copies would be useful.
I love the Spell Compendium. Yeah, I too have most of the spells in their original sources, but the revisions and collecting them all in one place are a major bonus to me. I HEART the Spell Compendium.