Despite claims in the 14w29 snapshots, the lag issue persists. The world seems to generate notably faster than before, but this has not impacted the lag for me. Every couple seconds I experience lag-related freezes that render the game impossible to play. I was able to remedy the issue by reducing the render distance below 10 chunks (anything 10 or above had no noticeable impact), but my computer has never had an issue running at maximum settings with 30-40 fps.
Lighting and other graphical settings had no impact on framerate.