I can confirm that the update for FCP X 10.0.1 is 1.44GB. On my Mac Pro I had to use Timothy Payton’s timely trash-and-install solution: a million thanks to him.
On my Macbook Pro the update button was waiting for me and it ran to the full 1.44GB which took only 9 minutes to install. For the record the MBP update was done after using the Timothy Payton solution.