Junk apps have taught me that a spinner that takes too much time could be an indication of failure though. The user will be inclined to refresh or close the app.
Same, but only if it "looks like" the app expects it to take a short-ish amount of time. If your operation will take more than a few seconds, the app can include text saying "This usually takes a few minutes" (or whatever is appropriate), and I'll know that a long of a delay to expect before I think something's wrong.
