I have started getting the inevitable question that comes with any new technology (in this case WCF and WF) - How fast is it? ... or more accurately: "What are it's scalability and performance characteristics".
I am yet to actually come up with any sort of useful answer to this because the answer is always "it depends" .... as in "it depends how you design, build and host your workflows / WCF services".
While I realise this is about as useful as answering the question "how fast does your car go" with "it depends how far I push the accelerator down"... I have come across some very good articles that attempt to address this piece of string question. And at the risk of committing the cardinal sin of answering a question with a URL.. here are some URLs...
These are quite an interesting read... although nothing super surprising, it is comforting to know we are moving forward in the distributed coms space (if you ignore those pesky primitive message payloads :-)