I did make something work once, just like you're leaning towards it was only using javascript and some classes on xform fields. It wasn't pretty and there was no data being saved between steps.

The new Episerver Forms that just came out has a built-in "steps" feature.

Upgrading to CMS 9 just to get the new Forms feature is probably not on the agenda :-)

If your editors have a requirement to be able to build new multi-step wizards themselves, I can (sort of) understand why you'd go with XForms. However, you'll be putting yourself through a world of pain. The times we've built multi-step forms in CMS6, we did them as page templates (not XForms), using either a system of populated placeholders that are shown/hidden depending on the current step, or using a standard ASP control like <asp:wizardstep

In our case, we had several integrations which had to execute and validate on and between form steps, so XForms wasn't the best choice. Then again, once the forms were built, editors couldn't easily change them. Bottom line, Xforms were never meant for multi-step forms - especially whenever integrations are involved. 

Benefits of upgrading should be repeated as often as possible :)

And why not also mention just going with Surveymonkey or similar. Not sure which ones can be embedded nicely if that's a requirement though.

Here's a really low-tech suggestion: In the first form (step1), setup the form to redirect to another page on submit (be sure to set the submit button text to "Next" or similar.)

On the second page, place your next form (step2) instead of a thankyou-message like you normally would. Repeat this chain of forms for however many steps you need, which for the user will seem like a wizard-type form.

Yes, you'll end up with a bunch of submitted forms data that you'd have to stitch together afterwards, so it's probably not the most practical approach, but it's an approach that doesn't require heavy customization :-)