We have a report that we are using the pivot table to publish all our goals and epics. Within the report in Aha!, the header is fixed as you scroll down. However after it has been added to a presentation and viewed in a web page the header is no longer fixed. So now when we scroll down to see the other products you aren't able to see the timeframes listed as column headers.
This should also be true for list reports in a notebook as well.
Another vote for freezing the headers on reports- our notebooks are huge and the reports really need to have the headers frozen for context.