I've used Hotwire a couple of times, and while you *do* have to be flexible in times, I've never had a problem. I used them to fly to CA for WorldCon, and my plane left at 6:45am, but all was smooth. Same when I used them to fly to Germany. The price to CA was excellent, and Germany was... not exceptionally cheap, but about fifty bucks or more better than everything else I'd seen.
Flying to ATL, it looks like I'll have to hold out for a sale to get something under $200 that doesn't involve a stop. I will happily pay an extra thirty bucks for a nonstop - it's only two freakin' hours, I don't need to stop in Charlotte or Detroit, esp. not coming back, when I'm exhausted and hungover!