iOS has always operated under the least effecient method here, at least until iOS 7 – and apps designed for it – come out. As it stands now when one app needs to get on the network, it simply gets on the network. If it finishes and then two minutes later another app needs to get on the network, that app does so, and so on and so forth.
The problem is that waking up an app and getting on the network is an energy-expensive process. Once you've got a network connection open, you want to use it as much as you need to, and then shut it (and, if possible, the apps using it) down. This is exactly what iOS 7's coalesced updates allows.
With a simple analogy, Hamilton does an excellent job of making iOS 7's coalesced updates easy to understand. Particularly in how they actually save battery life on your iPhone rather than using more of it, as seems more likely when you first hear of the feature.
I'm extremely excited to get access to this feature. No longer having to wait for apps like Felix, Tweetbot, Instagram and Facebook to load each time I open them will magnify Apple's goal of putting "greater focus on what matters most: your content."