I am evaluating WF for use in line of business applications on the web, and I would love to hear some recent first-hand accounts of this technology.
My main interest
It really depends on what you want to do with it. I've only used it a little, but compared to more mature products like MetaStorm (I know technically it's a BPM, but there is still a workflow component), Process Choriographer and IBM MQ workflow, there's no comparison. It's just not mature enough. On the other hand it's free where the others are not and can probably get the job done. I don't know if I would place a multi-million dollar operation on it, but with smaller ones, I'd give it another shot. The real hurdle you are going to face is the change in thought process it requires. If you don't have developers that have worked with state systems before that can be a real hurdle.