MyFaces amounts to a bunch of jars files. You add them to your project and off you go -- how could WSAD stop you? I've done it and it works fine. On the other hand, WSAD comes with its own implementation of the JSF (and its own set of extended custom components), so if you are working on your project in the IDE and select "new..." you will see choices "JSP page" as well as "Faces JSP Page". If you choose the latter it will start tossing its own jars into your project, as well as doing other things like defining a backing bean class. Similarily, if you are editing a JSP page, a pallete of tempting components may appear. If you drag and drop certains ones ... whiz! bang! ... more jars will be added and your jsp will be editted in subtle ways. Do you get the idea that I think WSAD has an attitude problem? A bit nannyish?
Anyway, I'm not a drap'n'dropper and I've managed to use MyFaces successfully, but I've just come back from a course on JSF. (Typical. either I get sent on courses I'll never use, or never wish to use (BPEL, shudder), or courses that come a year too late...) Anyway, I asked the instructor which version of JSF he recommended and his reasoning was: if you're developing in WSAD, use the version that comes with it, since that is likely to be better supported, although you may want to avoid any components outside JSF's core, since that would limit portability, if your were to switch implementations.
Is that good advice? How good is the JSF implementation that ships with WSAD 5.1.2? I don't care about drag'n'drop support or other IDE hooks since I hate them all, but just on the industrial-grade standard, how does it compare to MyFaces?