I think a chunk of fixing old ones can be done "manually" via search/replace processes. If you use MS Word, you can use "^p" (without the quotes) to find the newline characters Christian mentioned. So then you're search / replace commands would be:

^p --> [/TD][/TR][TR][TD]
| --> [/TD][TD]
{table] (or {table=head])--> {table="class:grid"][TR][TD]
[/table] --> [/TD][/TR][/table]

I think that would cover most of it, barring lots of column spanning and such.

When I was playing around with it a few weeks ago, I found the interface to be very similar to creating a table in Word, actually. You press the button, you get promted for some details including how many columns and how many rows. You can add new columns and rows via buttons on the toolbar; you can also add a new row to the end of the table (I believe) by presing tab while in the last cell.

If you were to opt to go with text-mod input (like what we have here), you have the benefit of being able to cells from a row on multiple lines of input. For example:

        [TD]Cell One[/TD]
        [TD]Cell Two[/TD]
        [TD]Row two, Cell one[/TD]
        [TD]Row two, Cell two[/TD]
        [TD]Row three ...
and, hey! look! I can now have a
cell that spans rows
just by hitting my return key! 
*high fives everybody in the thread*[/TD]
        [TD]*takes a deep breath and calms down*
As a programmer, at least, I often find the outline-like structure helpful. Your mileage may vary, of course.