I am planning to write a windows forms application that requires multilevel approval in order to process something. Like Creator (Requester) -> Review (Reviews the order and escalates to next level) -> Clerk (first level approval) -> Manager (Final approval) -> Back to creator
Once Creator/Requester fills out a form and submits, I wanted to start a workflow which automatically fires emails and based on response it sends it to the next level.
That sounds like a process orchestration that WF4 is well suited for. In general I would recommend using an IIS hosed workflow service and let that take care of all processing.