Forms usability

I was wondering if any of the list members are aware of any useful / quality 
analyses of the usability of online and offline forms.

I am asking the question in the context of some issues I am thinking through 
about XForms but my question is looking for information from other contexts.

I am not particularly looking for glossy reports on usability or complete 
books (although I would be interested in any pointers to those if they 
exist). I would also be interested in anecdotes of doing things right or 
those "Ah ha" moments when you realise why customers are moaning about a 
particular form being a pain.

If there are any publicly accessible explorations of usability of forms on 
smaller-than-desktop user agents that too would be of interest to me.

Thanks.

Andrew Watt