I've enabled it in every game I've played since the early 2000s, purely because screen tearing looks really awful and disabling vsync does absolutely nothing to increase my frame-rates.
I've been to several LAN parties recently and many of the gamers there swear by keeping vsync off - and they somehow don't notice the screen tearing when it's very visible to me on their screens. They also suggest turning vsync off if someone gets a lower-than-60 frame-rate, which again, makes no sense to me. Disabling it has never increased my frame-rate in such circumstances.
Maybe vsync mattered more in the CRT days? (I can't remember, it's been almost 10 years since I had a CRT monitor)