Any update on API (Flex 3.4, JavaScript 3.6) supporting WFS?
... you might want to add your vote to http://ideas.arcgis.com/ideaView?id=08730000000bteYAAQ ("Add a WFSLayer to the web APIs" created by Mattias). Also, specify if you're looking for read-only access or WFS-T (transactional support). The latter is more complicated. Also, which sort of specific WFS servers/software you need access to, because different WFS implementations tend to be a bit different from each other, making it hard to support all possible flavors.