[eluser]Colin Williams[/eluser]
What you've done is, with the support of a flawed semantic argument, replaced superfluous DIV markup with superfluous DL, DT, DD, OL, UL, LI markup. Forms aren't "just definition lists for which the user must provide the definitions," unless of course the form is part of a dictionary creator.
When you ask a user for their username, you aren't asking them to define the term 'username.' You are asking them to
provide or
supply their username. Clear difference. This is why there is a LABEL element for form controls, not a TERM element.
Also, just because a form may be laid out and meant to be completed in a sequential matter does not necessarily make it an ordered list. I think the same thing holds true for unordered lists. Think about a list of paragraphs. You wouldn't mark that up as <ul><li><p/></li><li><p/></li></ul>, would you?
I don't think any of these methods are necessarily wrong or bad. The more hooks CSS has, the better. I just don't think there's a strong semantic argument for any of them.
The vagueness of the humble DIV element lets one create their own suitable semantic structure. Using meaningfully classed DIVs, in my opinion, is much better than stretching the definitions of other inadequate markup elements.
