I notice the tearing and it impacts the image quality substantially I would rather not suffer it. Equally I notice the jaggies without AA but the performance impact is normally pretty dramatic.
I was fine up until about 2003, I was happy with 30 fps or so on a 85Hz CRT with vsync. Then I started playing more and more competitively, first Counter Strike and then a European Championship in Call of Duty. I found dropping the quality, increasing the frame rate to 60 (LCD by this point) improved my game a little and then removing vsync also further improved it. I couldn't really see the difference back then, I could feel it but not directly see it.
Fast forward nearly 10 years and the difference between 30 and 60 fps is now enormous, and I am finding 120Hz is a suitable advancement over 60hz. While I no longer play at a competitive level and haven't won a championship in years I still need that level of performance to feel the movement in the game is attached to me. I can see the animation moving at 30hz, even if its only momentary like with vsync and anything below 60fps. When vsync is on it feels detached from what I am doing, the latency from input to the movement is easily noticeable in comparison to vsync off. Thankfully I don't yet feel the need for 120 fps, a minimum of 60hz is what I am aiming for, but consistent 120hz improves my game, its just not really realistic to get at it consistently.
Ultimately I want a card that can do 120Hz reliably with decent graphics and not get the additional latency of SLI/crossfire and I also want to reduce the context queue. I don't yet know where my threshold lays but I doubt I am at it yet, games certainly don't yet feel smooth.