Additional information:
Traditionally, the IRS does not open up e-filing until the last week of January at the earliest. There was one year where they didn't open it up until mid February. So completing your taxes before the IRS opens e-filing will not be of much benefit.
Also, e-filing before the IRS "officially" opens for e-filing means that your e-filed return will be stored on a server and just "sit there" until the IRS is ready. If during that time you realize you need to change or correct something, then to bad. You can't do anything until after the IRS either rejects your return, or processes it.
It's also common for the IRS to pull a few test returns "before" they officially open e-filing. I have never in my life seen a test run of "anything" go perfect the first time. So if your return gets pulled for a test, you risk the possibility of it being lost permanently and forever in the IRS system. Then, when they IRS says you did not file a tax return and assesses late fines and penalties, good luck proving you did.
