So there are many suggestion threads regarding food and population, but I would like to present a very simple problem related to the two: player intuition and the food mechanic. When I started playing in BETA 2, I discovered that my cities would plateau in population, and advancement would not be possible without additional food. Unfortunately, other than building that initial food producing tile, I had no idea what to do. I now know that it is extremely important to build near a food-rich tile (fertile ground, particularly) as early in the game as possible. I do not consider this mechanic to be intuitive or fun for new users. I feel forced to seek out a specific tile before founding my city, and I know that should I fail to do so, my progress will halt temporarily or indefinitely.
Either make it very clear to new players that they must find food tiles early, or change the mechanic. As it is, I don't find the food/population cap system fun or challenging. It feels too arbitrary: "Find X tile early or fail." For such an open and dynamic game, such hard rules (which are unclear to new users, which compounds the problem) weaken the experience.