a GUI [..] a-la IIS Management applet in Windows
Not an answer to your question, but especially when moving things from one server to another (like you kind of did when you installed Snow Leopard), or when taking things from a test machine to a production machine, I think you'll eventually love the configuration files.
In the IIS management console there's all kind of settings on many different screens, or hidden behind some "Advanced" button. One cannot get an overview of all current settings. And even worse, with each new version of IIS (even with a Service Pack) a few defaults might change, which one will not notice unless going through all the screens and buttons.
For Apache you can see and edit all settings in a few files.
So, and I am not trying to be funny: a good text editor might be the best GUI you'll find!
(I have written IIS configuration manuals that got outdated faster than I could create new screen captures; for Apache I'd just copy the relevant parts of some configuration files and that would be it.)