I guess I'll be the contrarian here, but their old site was kludge but at least they had stuff in stock. I've ordered a few times from Wig Wag in the last couple of years and it wasn't any more painful that ordering from N Scale Supply.
I don't care how slick your interface is if you only have what just came out of the shipping container in-stock for a week. I've got a local guy who can order that stuff for me at a good discount and I don't have to pay shipping from Maryland.
The whole reason to mess with a legacy shop is to find stuff you didn't even know you wanted when it came out.
One new style online vendor that gets it in my opinion is Midwest Model Railroad, they always have staple items (like Kato wiring components) in-stock, have aggressive prices and ship super fast.