Originally Posted by mpomfret
I guess it depends how heavy your bags are, how much you want to save money and how tired you are. You can use the subway quite easily: From Tokyo Station catch the Marunouchi line to Ginza, change to the Hibiya line and that will take you straight to Roppongi (Grand Hyatt). 4 in a cab should be fine, but might cost you a few thousand yen.
Just keep in mind that the "transfer" between Hibiya and Marunouchi at Ginza is over 600 meters apart. Also, the walk from the Hibiya line at Roppongi and the GHT is no cakewalk, 10 minutes up and down. A taxi will cost you 1500 yen. Four subway tickets will cost you 720 yen. Take a cab.