If I open a new spreadsheet (without a template) the default behavior is to convert data types to randomness. Some numbers are interpreted as dates, and so on.
Not only that, but frequently, having converted it, I am unable to reset. Instead Excel will display #ERROR or some such nonsense, even though clicking on the cell will show the original data in the toolbar area.
Please tell me you understand why this is a design flaw. The default behavior for an application like Excel should be to preserve data, not convert it. Just as the default behavior for a Word Processor should not include making decisions about how I want text formatted without me explicitly formatting it - changing font, indentation, line spacing, etc. Yet, Microsoft Word does this too, and then doesn't even include an option to show me what formatting codes are responsible, so that I can remove them, and restore the text to un-formatted.
This is simply crap programming from MS, as per usual.