Yes I have tested some of the best phones in the market and there is still that minimal lag, not enough to be noticeable by non-photography obsessed people, but enough for me to miss important moments if I relied on the smartphone camera to do any critically timed shooting. Oh you would not believe the "marketing" phrases, using "laser-assisted AF, Phase Detect, X-ray scan, heat vision with whatever crap alien AF technology" yet when it matters, the AF misses, or the camera just lags.
I'd take a fully optimized 8MP image sensor with optimized per pixel sharpness, good dynamic range control as well as decent high ISO performance (usable ISO1600) over a half-baked, over-hyped and honestly disappointing anything over 20MP image sensor on such a tiny sensor for a smartphone.
Amen. This is a good read overall.