I think it probably is a tragically uncommon thing for DMs to utilize the intelligence of the monsters, but it all depends on the DM. I, for one, definately play intelligent monsters with intelligence. I like to have monsters set ambushes, traps and actually have battle strategies when appropriate. I also tend to have intelligent monsters retreat or surrender when the odds prove to be against them. A smart monster isn't going to fight to the death unless he fears retribution by his master (if any) more than death itself. Every moment the monster spends alive in surrender is another opportunity to get the drop on the PCs or even manipulate them into aiding the monster without them knowing.
I also like to play some monsters "heroically" on occasion. By that I mean the monsters have champions of their own who will do dangerous things to protect their kind or their agenda. Some monsters will sacrifice themselves to allow others to escape or will distract the heroes so that their plan can be uninterrupted. Monsters have heroes too, albeit with their own (if skewed) view of the world.
HARRY DRESDEN — WIZARD
Lost items found. Paranormal Investigations.
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