I haven't got the 3.5 books, so I had no idea they added these kinds of descriptions to them creature entries.
I like the idea IN THEORY, but I from what I've heard in this thread, it sounds like they bungled the idea. Flavorful, narrative descriptive text that a newbie DM can read verbatim is good, as long as it describes the creature's appearance and attitude in a useful way. The examples I've seen here aren't useful. I'll have to take a look at the book in person now, though.
I like the round-by-round tactics for the tougher monsters, even though I don't really use them. The descriptive text sounds like the same kind of mentality, but a poor implementation.