The other thing I've also notice it that HAS is very reluctant to pinch hit for anyone batting in the meat of the order. Best put your platoons at the 1 or 7-8-9 spots in the lineup. Put your platoons there, and I've had real good luck with HAL switching out your platoon guys late when the game really is in question.
I agree with many of the above posts. Most time your don't want to swap out guys when your opponent changes his pitcher before the 7th inning or so, so HAL is actually doing you a favor here. ;)
But, platooning can be absolutely key to winning if you don't get the guys you want in the autodraft, and even then I often draft specifically for certain platoons.