I don't personally own any Madewell stuff, but there is a store here in town, and I've been in a few times.
Madewell is owned by J. Crew. Mickey Drexler (J. Crew CEO) used to work for the Gap, and he's the one who came up with Old Navy. When he moved over to JC, he wanted to start the same sort of thing for them. So Madewell is more casual and slightly less expensive than J. Crew. Like I said, I can't really vouch for the quality, but I imagine it's probably okay, but not as nice as JC--ie, JC uses Italian cashmere and hand finishing on some of their garments, premium wools and denim, etc. Madewell doesn't do any of that. Madewell isn't as cheap as Old Navy is in comparison with the Gap, though, so I probably wouldn't call it "throwaway" fashion, either.
I'd probably check it out if I were you and just see what they have. Like I said, I have been in the store a few times, but I always end up just spending my money at J. Crew because I like a little dressier style, and Madewell isn't really dressy at all.
Not sure if that helped you. Maybe someone else has actually bought Madewell stuff and can talk about wear and things.