Lars Løge has reported a couple of errors with the textmode option in siunitx. One was rather harder to spot than the other, but both should be fixed in v1.2e, which has just gone to CTAN. I’ve also had some questions about table formatting with footnotes, but this is a ‘hard problem’ and I’m not likely to alter the current behaviour in version 1. It is on the list for version 2 (although I need to look again at pgfplotstable first, and see if it is worth the work).