not necessarily, it depends on how much output you are actually buffering and how many times you are doing it
many programmers use it, but i find it easier to just not have to use it
i did a few tests a while back and was buffering around 100 lines of output, and that yielded a less than .5 second of a difference, it seems for all the test, it yielded around 10-15% slower, but when you are looking at milliseconds, or even seconds, that isn't much to worry about.