I don't fly WN, but I believe they offer a compelling product to the flying public, especially to ones who do not have status in other major airlines. If you don't fly a lot, you certainly like the free baggage allowance, no change fees, and who care about the "kindergarten" boarding process.
I can't argue about whether they started the race to the bottom, but they are certainly not a bottom feeder airline (think NK).
i think they provide a good alternative flying experience to the flying public, and I believe it is good for the airline market.