My son, who's four next month, adjusted really quickly. The first couple days were the hardest, he kept pushing the power button on the TV (we have a switch that turns off the outlet so nothing happened) but he was easily distracted. Pretty much after that he didn't think of it anymore. The harder part was me - not using the TV as a distraction when I needed to do something, and expanding my repertoire of activities that would accomplish the same thing (like allowing me to shower or answer the phone). A month later and we're both fine, though.
The hard thing though is when we DO watch a dvd on the computer it starts those first two bad days (for him) all over again - for example: yesterday I made popcorn and we watched a national geographic flick. Today I made popcorn and he was adamant that popcorn of course mean more national geographic, right? No such luck, buddy