Gawd, I do pulldowns every workout. They aren't useless. Again, they are very helpful in the "offseason". The Hammer Strength lat pulldown machine is especially useful and allows me to use more weight than even my own body weight without worrying about hanging weights from my ass.
Chin ups = Good
Pull downs = Good
Beginners should be working on increasing their core strength anyway so, yes, do chin ups, but don't walk around the gym turning your nose up at those who don't.