Mark,
[I have not have read the entire thread in detail, but responding to one question.]
I'd especially like to hear from other people in the TCP community; we've heard from Joe and Michael; do others share their opinions, or have another view?
Responding to this specific question: I think this document is useful. There's tremendous value in having a document that discusses protocol interactions, especially for the most important protocol interaction today (HTTP/TCP). Pursuing this document as Informational makes complete sense, and is well within IETF norms.
Implementation notes/advice is actually quite a useful bit that traditionally shows up in appendices, but arguably it really doesn't matter where it shows up. It's valuable. I would remove specific APIs and instead talk about mechanisms that are common enough (remove setsockopt() and sysctls, but talk about Nagle, socket buffers, etc.) but there are a number of commonly deployed mechanisms that it makes sense to talk about them here. I would suggest that the document discuss important interactions from a browser's point of view as separate from those at a web server.
I am happy to review and suggest changes to the document, but I think it's a fine fit.
- jana