There's nothing that I can say about the MARCThing Z39.50 implementation for LibraryThing that isn't in the Thingology post. But this statement caught my eye:
I do have a recommendation for anybody involved in implementing a standard or protocol in the library world. Go down to your local bookstore and grab 3 random people browsing the programming books. If you can't explain the basic idea in 10 minutes, or they can't sit down and write some basic code to use it in an hour or two, you've failed. It doesn't matter how perfect it is on paper -- it's not going to get used by anybody outside the library world, and even in the library world, it will only be implemented poorly.Amen.