Well, now I can answer my own question, since I went thru MCO today!

Yes, there is a priority lane at MCO, at least for some airlines. JetBlue happens to be one of them.

It was a fortunate thing for us, because Saturday is apparently "Cruise Day" at MCO. The day on which many of the cruise ships are dropping off passengers and they're swamping the airport. The place was seriously mobbed.

It seems like it took us longer to walk around the regular security line to get to the priority line (it's on the far left side of the regular security line, heading toward the B gates) than it took to get through security in the priority line. Super speedy. The regular lines were packed and snaking around the usual rope maze and stretching around and into the atrium there. I heard people mentioning a 45 minute wait from entry to the line, to exit on the other side after screening.

Basically, if you're traveling through MCO, the "Even More Speed" that you get with the "Even More Legroom" is amazingly worth it, IMHO.

Good luck!