I recently spent some time rummaging around trying to figure out how to use the table formatting option.
There might be an explanation somewhere, but I couldn't find it. So here's how:
Arrange your text one line per row with the "|" character separating the columns. The first line will be the headers.
Header 1|Header 2|Header3
Then just highlight the area and click on the "Table" icon.
Your edit window will look like this
[TABLE]Header 1|Header 2|Header3
now hit "Preview Post", and Voila, the table appears in the preview window.
|Header 1||Header 2||Header3|