I feel like a GHD is a must have for anyone who styles their hair regularly. It heats up quickly and styles very well. It is sleek and small, and doesn't catch hair. It also has a function that turns the iron off after half an hour, so if you forget to turn it off, it will send out a regular beep to let you know, but will not stay on.
I had my first GHD for 5 years (which I battered and dropped regularly), and my second one for a few years as well. They last a very long time and are great value.
I've got really frizzy hair, which has been impossible to tame since I was a kid. After learning about hair straighteners, I have tried using so many different ones. The GHD classic is the only straightener which can straighten my hair properly, smoothly, and remove most frizziness. Easy to use, quick to heat up, and lasts for a ridiculously long time, I can't see why you'd use any other straightener!
Tips: Use a hair protectant spray!