Personally I have found Google Navigation to be really accurate. Estimated times are always really close to accurate if not spot on!
When calculating a route it takes traffic into account automatically. Combine that with Google Now = winning!
"Is life so dear, or peace so sweet, as to be purchased at the price of chains and slavery? Forbid it, Almighty God! I know not what course others may take; but as for me, give me liberty or give me death!"
-Patrick Henry, March 23, 1775