>>The NULLs require special handling in queries and in front end. My rule is not to use NULLs unless it's necessary:
>>- In datetime columns
>>- Foreign keys
>>- Any other case where NULL is significant (represents absence of data or N/A).
>
>Thank you for your input. How do you handle "0" vs. nothing in a numeric field (or is this one of the special instances)?

I would use (never had to) NULL if absence of data is not the same as 0 value.