I did my PADI OW in March of last year while in Florida on vacation and then went back at the end of October and did my AOW though NAUI. Both courses were excellent and very educational. I happened to be the only student both times and got to cover things more in depth and ask my instructors questions about anything that I may have had difficulties with. Like Eric_R mentioned earlier, you do several different types of dives and enforce things you’ve already learned. I happened to touch upon cavern, rescue and a drift dive. Had the ocean been a little more calm at the time, we would have done an intro to wreck diving and I would have also gone for my NITROX certification. Those will have to wait for another trip.
Trust me, you’ll have a great time. And don’t forget, no question is a stupid one. If you are unsure, please don’t forget to ask, because yours or somebody else’s life could very well depend on it. My best advise would be to go over your material from your OW course as well before hand. But first and foremost, have fun.