We are in the process of selecting a workflow solution for a company that uses Microsoft products end to end. Given the news on WF4, in that it seems to be essentially a rewrite
I, as a workflow developer, think that current version is painful to use. This is not surprising as this is a v1.0 software out from microsoft :)
I think you should first consider your expectations from a workflow software. Do you have a well defined list of expectations from WF? Acutally I am wondering content of such a list. Maybe we can help more detailed on each topic.