Koh Tao gets very quiet around the full moon, as every party person in Thailand heads to the world famous Full Moon Party in Koh Pha-Ngan, the island right next to Koh Tao. A popular option to avoid being room-less in Koh Pha-Ngan is to actually stay on Koh Tao and just take the FullMoon "party boat" over. The boat leaves here at 6pm, gets you right to the party beach by 7:30, and lets you go all night and then brings you back at 6am. No worrying about trying to find accommodation at one of the worlds biggest parties.
So if you're in to chilled nights on the beach with friends, or all night parties, Koh Tao does offer it all.