I'm really happy to read this. We flew a couple of weeks ago and I was amazed at how well SW handled the peanut situation.
I noted my DS's allergy online at the time I made our reservations, and while we had a fairly early flight going to WDW, I knew that when we were flying home, it could be an issue because it was a late afternoon flight.
When we checked in for our flight going to WDW, we were given pre-board authorization (for my DS and one other person), but since all 4 of us had EBCI and our boarding position was around A-30, I decided it wasn't necessary and just cleaned our area when we got on. There was actually a peanut between my seat and my DS's, but I just wedged a clorox wet wipe over it. Also, they gave me a card to hand to the flight attendant when we boarded, just to ensure that they didn't hand out peanuts and that they handed out pretzels instead.
On the way coming back, since we did RAC at our resort and didn't need to check our bags at the airport, I asked at the gate about that card to hand to the flight attendant. She was beyond accommodating and said we could all pre-board even though I told her we didn't have to do that. We had around A-30 again, but since she insisted all 4 of us pre-board, I took her up on it. While I expected to see more peanuts strewn around on this flight given the time of day, it was actually pretty spotless (still cleaned the area, of course).
The pretzels they serve actually have a cross-contamination warning, so they're not safe to consume for peanut/tree-nut allergic people, but they're not going to have a reaction from someone else eating them. Granted, people can still bring what they want onto the plane, but the fact that 75%+ of the people on the flight or previous flights aren't eating peanuts is huge in my book!