If the flight originates in your city, I don't think it's necessary if you arrive that early. If the flight is starting out at another airport and just adding passengers in your city, then your chances are a bit more iffy.
That said, I've never NOT been able to get seats together on flights to MCO, and our flights do not originate here. We normally use the kiosks about 2 hours before departure time. We don't always get A's, but we've never been last on.