I think it is very important to know any variations on how people may attack you. What has suprised me is the only explicit pressure point in aikido seems to be in yonkyo. I've often wondered why this is so, especially as so many of the techniques are ideal set ups for pressure point attacks. Although I'm no expert myself, I was chatting to someone who does shiatsu, and they were saying that the point for yonkyo (along the heart meridian) is often used to relax people who are stressed. Possibly this is why yonkyo is retained above potential knock-out or lethal points.
When we do striking practise, I always mention 'vital areas' to strike, just so people are aware of areas which they have to protect. However (except for some obvious ones around the neck, and a couple on the arms and legs) I think many pressure points (especially combinations) are hard to strike effectively with a vigorous and mobile attacker.