I'd vastly prefer to see new/updated monsters over a book of monsters with levels. (For years I wanted stats on the Molydeus from PlaneScape! Of course, now I have it, but I digress..) While it does reduce work for some DMs, this game has made applying four levels of rogue/fighter/etc comparatively easy. Two feats, some BAB, some saves, the hit points, and you're done. For a combat monster, I don't bother with skills, unless I think they'd have ranks in Listen/Spot/Search/Tumble. (Combat) Monsters are for killing, and "Profession (architect)" isn't something I need to worry about.
For anything that would have 10 levels of wizard and some of archmage, for example, that ought to be fully statted out by the DM anyway, as that's approaching BBEG level. An NPC like that deserves the full treatment.
Also, when you use example classed monsters from established books, you run into the problem of the player who has read the book cover to cover, and knows it all regarding that monster. I used classed monsters personally as a way to thwart those players that did that. I'll never forget the satisfaction I felt at seeing the blood drain from my players' faces when I said, "The orc gets a dangerous look in his eye, and rages." Some may suggest that DMs could change things to keep the players on their toes, but then I ask, "if you're going to alter them, why have books of classed monsters at all?"
That said, I wouldn't have been opposed to seeing example classed monsters next to their original entries (the drow stuff from MMIV in the MMI after the drow entry). Even if it caused the MMI to be two books instead of one, doing it that way seems a lot more logical to me.