We just booked April 2006 for 5 of us, PHL to MCO, with USAir. Rates seem to be all over the place. Like you, I only wanted early morning departure going to MCO and late departure leaving MCO. I watched travelocity for about a month before I finally booked. I checked USAir's web site and all the other discount sites, and found Travelocity had the most to offer and the best prices. After watching the prices for awhile, I just decided on what my "deciding" point would be. We paid $220 for Easter 2005, and I decided that if I could find $220 again for Easter 2006, that would be a good enough deal for me. I knew I was being picky with flight times, and I had no flexibility on my travel dates, as hubby is a teacher.
I refused to buy until I saw that price, and I was fine with waiting until SouthWest opened up their dates if I had to (which they still haven't).
I'm thinking SouthWest and AirTran will definitely have better rates than $600, but I'm sure either of them won't open their dates for May 2006 until at least January some time.
My suggestion would be to wait...keep watching Travelocity, Expedia or Orbiz, and if you find a good price you can live with, then go for it. Otherwise, you can still wait for SouthWest or AirTran, which I think would definitely be better than the current $600.
Good Luck!!
ETA: Oops! I read that as $600 per person!!!! Whoops! $200 per person right now is pretty good...but SW might still give you a better price. Just need to be willing to wait.