Do I need to file a 1040-ES?

I was unemployed 1/2 of 2005 and all of 2006. I began working for an LLC in Jan of 2007. Taxes are not taken out of my paycheck. My question is, do I need to file a 1040-ES? There is an EXCEPTION listed on the first page of the form stating that if I had no tax liability for the full 12-month 2006 tax year - I do not have to pay estimated tax for 2007. I am married filing jointly, does that have any change in the situation? Where can I get a definitive answer so as to begin making estimated payments or not have to worry about this.