The son of astronaut Chris Hadfield set up and moderated a Reddit thread for his father and selected questions for his dad to answer. Here are some answers that give you a good feel of what it's like to be an astronaut:
On what it's like to float:
"It is the most amazing experience you can know. Once you get over the sickness from your inner ear getting used to not having an up or down, that is."
On how similar is it to floating in a pool:
"Imagine floating in a pool without water, if you can. We train in the pool because it is the closest approximation we have on Earth, but nothing can do it true justice. The inner-ear problem comes from your body no longer having a judge of up and down. Without an up and down, your balance becomes out of whack, your body thinks you're poisoned, and you vomit. Makes the first day less enjoyable."
On physical requirements:
"The requirements for going to space are obviously rigorous, both physically and mentally. Physically, astronauts are expected to be in top shape. There are also height restrictions (due to shuttle and suit sizes). My background is in mechanical engineering, and I was a experimental test pilot before getting selected."
On his thoughts before taking off for his first launch:
"Launch is like being shaken in a huge dog's jaws, while pushed from the Earth by an unstoppable unseen giant force."
On some of the cool geological features of Earth seen from space:
"Lightning at night is awesome — thousands of kilometers of arcing light and power. The Bahamas are stunningly beautiful — so much gorgeous shallow reef, all the hues. I like seeing meteor craters, visible reminders of Earth's place and past. And hurricanes are huge, like Jupiter's red spot."