In contrast to sentiment of many replies here, I have really enjoyed my PhD (admittedly I have not yet submitted - I plan to in the summer). I worked for a year prior to starting, and while that was fun, it felt very limited by comparison. Being around smart people who are interested in a variety of topics, and have the freedom to pursue them, makes for an amazing environment. I've learned a huge amount, and I think the tradeoff of low pay for a few years was easily worth it.