When should I be using DL/DT/DD elements ? They appear to be designed for dictionary type usage. I've seen them used in situations I would hardly call dictionary usage though.
You can use them for FAQs.. <dt>'s around the questions and <dd>'s around the answers. And one may argue it's right to use <dt>'s around form labels and <dd>'s around inputs/textarea/selects.
As a general rule, it's good to use them when you have a list of items, where every single item needs a title An example might be a list of different species of the banana plant, with the scientific name of the plant as the DT and the description as the DD, all surrounded by a single DL
I wouldn't use them for marking up form controls, period. Other than that, you're right. It's a definition list, and is thus best used in FAQs, glossaries and the like.