Just one suggestion, if your "default" subs get large, it is usualy a good idea to convert them to 'builder' methods instead.
Oh, very cool. I'd missed the builder bits while reading the docs. It does seem like a nice shortcut, and I kind of like the additional semantic alignment. I'm actually building the value, not setting a default value. Granted, it doesn't make a practical difference. But when there're two ways to do something, and one of them is a better semantic match, I usually choose that one.