If this is the only Web application you'll ever write, then it's a good question. However, if you plan to write others in the future, then it's definitely worthwhile to find and learn a good tool to do the job rather than attempt to roll your own.

Yup.

Catalyst is dead easy. I mean, if you really want simple, go use one of those sites that create a survey for you and use that.

But Catalyst will help you create code that's maintainable and scalable so you can reuse it over and over and add on as you please.

Okay I'll definitely give it a look but I'm really not looking for scalability for this particular application (the need for generality may rear its head in the future, but I can't predict it will).

The reason I don't want to use those sites (I looked at Qualtrics) is I need to implement some more complicated server-side computation in the dynamic elements, and from what I can tell I would have to rely on javascript.