I love mcmaster and it's cool to see an article explaining their website design intent. Recently discovered Digikey and Mouser last night (via a random HN comment actually) and it was just what I was looking for (a more electronics focused Mcmaster basically) - but the websites have a similar filter/taxonomy which was refreshing to see. No B.S.! I do have some business/commercial reasons for shopping these vendors (which is how I'm familiar with mcmaster in the first place) but my life really started to change for the better when I started leveraging them for personal projects.

Had a kick to make biodiesel and mcmaster was still the best place I could find to buy methanol

Edit: mcmaster just exudes the essence of "engineering" to me - it's amazing to be able to find parts by their size/dimensions/material/finish rather than jumbling together things that "work". Reminds me of the joke: "a mathmagician calculates the volume of a ball by integral; a physicist calculates the volume of a ball by water displacement; an engineer just looks up the part number in {mcmaster}"