There are at least some cases in modern client-side programming that you have access to progress information, and would therefore want a progress meter rather than a progress indicator. "Use spinners for everything" strikes me as short-sighted and reactionary advice.
You get a progress meter when you're pushing data, like uploading a file. And that makes perfect sense. Use a progress meter here, it makes sense.
This is totally different. It's explicitly saying that it might be used with pjax or turbolinks. I don't think there's a way to accurately determine progress information for one of these, the best you can do is use historical data and guess. In this case I think using a progress meter is a bad pattern.
For instance, there's no way to monitor the progress of sending an SMS message, yet the iPhone UI displays a progress bar for it. It assumes that SMS's take an average of 4 seconds to send, so the progress bar moves at that rate.
NProgress follows the same idea, and its default behavior operates similarly. Ideally, you should tweak the progress to be more in tune with your average load times (which is what I've done for our 2 apps that use it).
