Iterating over Numpy arrays is non-idiomatic and quite slow. In all cases, a vectorized approach is preferred if possible, and it is often possible.
Numpy arrays are not a replacement for lists that you just drop in and everything runs faster. Numpy arrays are a commitment to doing things a certain way. If used correctly, Numpy arrays can be blazing fast. If used naively, they make things very slow.
This article discusses making a GIF which fades between three different images of different ideal color palettes, using Numpy to determine the transitions.
From time to time there are situations where it is helpful to quickly rip some information from a group of web pages. For example, I was doing some keyword analysis and wanted to know how many Google results there are for each keyword in my list (both exact and broad matches). The answer is right there on the page when you do the Google search, so all there is too it is to automate the process of doing queries.