databases and XML

Hi List, I was wondering what strategies people are using to handle large volumes of XML data: How do you store the data? e.g.: Text-files, databases (which one)...? How big are your datasets? e.g.: MB, GB, TB...? What do you use to query the data? e.g.: PHP w/ text-files, SQLServer with "for xml" clause...? Finally, what limitations do you experience currently when handling XML? Thanks in advance, Yves