What I said about Wordpad using an XML Format:
Somewhat incorrect.
It still defaults as .rtf, however, it has the option of saving as OOXML Document.
As for the registry being efficient:
I think its fine for Windows, however, if a program just puts the ini file in its own directory under "Program Files", thats when I would be happy. Its horrible when they end up all over in system folder, and windows, and under other ini files.
My biggest problem with the registry is the sheer fact that if part of it is lost, it can render an even larger part useless, which makes it more susceptible to corruption.
Also, its loaded at startup, and on older slower computers, that can take a while.