I used a poly/rayon/lycra that (for reasons unbeknownst to me) is also known as "Sophia" knit. This stuff attracts every piece of lint and pet hair within a 20 foot radius. But it's heavenly soft to wear. Since I'm planning to wear these only around the house, it's fine. I wouldn't use this fabric for a nicer garment though.
I cut a 38 based on my measurements. The fit is snug but not tight, I think it's just right. I didn't make any alterations, but looking at the pictures, I could afford to shorten the hem and inch or so.
The waistband is designed to be folded down over the hips. It's shown this way in the "All Styles at a Glance" section of BWOF.
With only 3 pattern pieces, you can have these pants traced, cut, and sewn in a matter of hours. This is exactly the kind of thing I love to wear around the house. I can see myself returning to this pattern over and over.