For example, first look at a screenshot from Apples native Mail app. In this screenshot on my iPhone 4S I just refreshed the inbox:
Note the space held by the persistent status bar in the bottom, the temporary space held by the loading icon below "All Inboxes", and the doubly redundant loading icon in the status bar.
Now contrast that with Mailbox on the right, in the same state of refreshing the inbox:
Active feedback is provided consistently at one location in the status bar, conserving precious real estate, while still displaying the standard status bar information when in it's neutral state.
Personally, I also found that Mailbox's less intrusive status indicators invited me to continue interacting with my inbox, regardless of what state it is in. I never thought of clicking an item or writing a message in Apples Mail app while it is loading. Instead I find myself staring at the loading indicator waiting for it to finish before proceeding with my business.