I concur - Having just had the interview yesterday my personal experience is that if you have a straightforward case (few vacation-type trips abroad, few employers, no issues with Good Moral Character) you do not need to take lots of documentation.
The reason is: if the IO wants to "dig" a little more it would not take you long to make photocopies of whatever is needed (for example letter of employment). The point is: I saw yesterday at least one person running to the neighboring Walgreen's just to take passport pictures and running back into the DO; for this type of minor stuff I think that the USCIS has understanding and allows to bring this type of document within a few minutes or hours (same day) if it is all what is missing to complete/adjudicate the case.
This being said, if you have spare time, you can voluntarily gather some additional documentation if you feel like it.
On second thoughts, I did not take my SS Card along, preferring to have with me the last tax returns as they are government-issued documents showing my SSN. The purpose was not to show evidence of employment but evidence of SSN if needed.
Just my 2 cents.