Burr,
As a rule, unless there's a true burning need to have data that is hierarchical (i.e. some sort of parent child relationship), then xml is almost always overkill. Ini files are dead simple to parse, there are dozens of readers for them (in terms of code libraries) in most of the major programming languages, and they are easy to read and edit by hand. XML pretty much fails at all of those things. Since ini is just a text file it's also portable to pretty much anywhere.