Typically I style forms with the unordered list tag e.g.
The key things that the W3C lay out for forms is that the Form is set up in a way that the labels and form elements can be easily grouped programatically:
1.3.1 Info and Relationships: Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text.
In particular HTML Technique 44: Using label elements and HTML Technique 71: Providing a description.
The advantage you get from wrapping each label and input in a list item is that the user with a screen reader may well get some indication at the begining that the list has x items in it, which might be useful.
Generally though our designers are with Zack - our form rows are wrapped in a div, with a class of "formrow" or similar.