Diego Doval's review of blogging APIs (via Evhead) overlooks the fundamental problem with XML-RPC in relation to blogging APIs: the inability to pass strings which are not restricted to 7-bit US-ASCII. I know I keep banging on about this but it can't be swept under the carpet for whatever reasons people have. The two obvious solutions with respect to XML-RPC are to encode Unicode strings in some way which is valid according to the XML-RPC spec, for example using the base64 XML-RPC type, or to transition XML-RPC to allow strings with a Unicode encoding.
The comments attached to Diego's post contain an attack on myself and Sam Ruby, one of the criticisms being that we're not really looking for an answer. Actually the post of mine being referred to is a suggestion about using WSDL for improving interop with XML-RPC. It may be a crap idea but it was an attempt to suggest a solution to a real problem. By the way, I just re-read the post and failed to see why anyone would think I was "annoyed" when I wrote it.