Okay, here's some things you should know!
Yes, you can print your boarding pass at home!
They may change your flight time but usually it's no problem for them to switch you to a flight time that you see fits you better, I think within 24 hours before or after your flight time. It could be by 5 min or 3-4 hours or total cancellation! Not always convenient, but at least they work with you on it. If nothing works for you they will refund your money if your request that instead. I haven't had them switch my times more than maybe a half hour and the flight times stay pretty steady it seems, at least here for what I've kept an eye on. I like them enough to keep flying AT, they have some great fares compared to other airlines. I just keep checking often, at least once a day, to keep an eye on flight times. They aren't the best at notifying you right away, but they usually eventually send you an email to accept or not the time change. Most people want to know right away to get the best choice of times to choose from before they get booked up.
Oh, and they charge $6 to choose a seat assignment prior to 24 hours to your flight. You can wait til 24 hour mark and then choose for free from whatever is there then. They charge at least $15 per first checked bag, (though someone said 20 the other day so Idk about that), $25 the second.
If you are traveling before 12/18 (I'm going 1/2/10 of course, so this stinks for me, darn it, lol!) they have a $25 coupon you can use towards the fare. Find it here: airtran.com/sunshine . If you book each way separately, use two separate email addresses and you save $50!
You may know lots of this already anyway, but you did ask for things you should know! So, hope some of this info was helpful!
