Barb--
I flew out of Chicago 12/1 on Spirit. Like I said above, my experience was great!! My flight left at 10 am and I arrived a little after 8. I spent about 25 minutes waiting in line (I started at the end of the turnstile area). Our flight left a few minutes early, actually, and we arrived into Orlando 20-25 minutes ahead of our scheduled time. The crew at the check-in desk were very friendly and speedy. While in line, I spoke with some others who had all flown Spirit before and they related that they had always had speedy check-ins and on-time departures. I'd definetly fly them again!
If you do fly them, they flight out of Terminal 5, the international one. When DH was dropping me off, we didn't see it on 1-3, so we thought we had just missed it. He dropped me at 2, so I'd be halfway between wherever I needed to be, once I checked inside. Too bad I had to go all the way to 5!! But that terminal was dead compared to the others, so that was nice!