While XML makes data more portable, it causes increased bloating at the same time. Especially with log file data. If you have a lot of data in a perfectly readable text-based log file (which likely compresses really well with gzip or bzip), why quadruple it's size by converting it to XML? XML is more useful for non-regular data, where significat meta-data is required to interpret it. For log files, which are highly regular, a few comment lines at the top can provide all the information necessary for parsing the data. e.g. http://www.w3.org/TR/WD-logfile.html
A more useful application of these technologies would be to analyze and summarize the data in the log file and then write a summary report to XML.
This report could then be processed with XSLT or other style processor to produce output in HTML, PDF or any other format of choice.