I think I use tools like Divvy http://mizage.com/#macdivvy more than I use the zoom icon, it makes it so much easier to position windows..
retailmenot also claims a $20% code, so that will knock some money off. But I happily paid retail and I use it 100 times a day. It's also particularly helpful if you use an external monitor at your desk and regularly resize windows as you attach or detach the monitor.