Update 7/19:
(1) The Spirit flight from Rochester was totally fine. I bought an exit-row seat and a checked bag and WiFi. The plane left on time and landed early. So early that the gate wasn't ready for the plane yet and we sat there for about 10 minutes waiting.
The seat was fine, the flight was uneventful, and I'd have no problem booking Spirit again.
The WiFi? Not possible to access, so I got a refund. That was not easy but I somehow gathered the 7,000 details that Spirit wanted in order to refund me the $11.99. Hey, it's $11.99 I can spend in 2 seconds at WDW!
(2) As of this minute, I have still not received any written confirmation from JetBlue about my refund, no refund is showing up in my JB cc account, and the last time I looked on the JB site, my itinerary is listed as the return flight and the price is the cost of the entire round-trip fare. No minus anything.
Supposedly JB will write to me within 24 hours of my lengthy phone call to them last night, and the clock's ticking. I'm having a hard time believing that they're going to respond after East Coast business hours, but I hope I'm wrong. And I don't care if they ever write to me, just give me my money back!
But here I am at WDW at a beautiful pool-view room at AKL. Hurrah!