It's Not That Bad
I must humbly disagree.
Have you ever tried to use the web sites of other carriers. Many do not let you search by fare (as US does). Many try to stick you with undesirable itineraries and won't let you play with them to find a more appealing option. Many are simply not visually appealing.
The US web site is by no means perfect and can be fussy at times. However, I think it is by far one of the better sites out there. I just hate AA and UA's web sites. WN has an excellent web site that is easy to navigate but it is not without it's faults as well. If you are more concerned about your web site experience than being forced through an airline like cattle then by all means enjoy your flights on WN to PHL.
As a side note...I was under the impression that US was planning a complete overhaul of the website in the next month or two. Was I wrong about that?