As a frequent business flyer on the US3, WN will still be a pass for me for the same reason B6 is: No Domestic First Class.
On a 737, no matter what they call it, no matter how much legroom they give, these are still going to be horrid 17" wide 3-3 seats.
Southwest should rip out the first 10 rows and put in a proper first class. I would pay extra for that and fly them. I do like the airline and I would love to fly into the alternate airports they serve (Midway, Hobby, Love, etc.)