When I did IT work for my university, I was in charge of a big plotter printer that the science students used to print posters with summaries of their research for conferences. The only format I ever got was PowerPoint. Based on the number of search results for "powerpoint research poster template", it looks like this PowerPoint is still the format of choice.

I never really thought about it, but it is kind of odd that the same community that loves using LaTeX for document formatting and typesetting research papers is also using PowerPoint as a desktop publishing substitute.