Last week I talked about app switching on iOS as if it were a totally solved problem on the Mac. It's not, especially if you bring app launching into the picture. There are several ways to open apps on OS X: the Dock, Spotlight, the Finder, and the much-maligned Launchpad. Rewind further to the classic Mac OS and you'll find the Launcher control panel, an application-switching menu and palette, and the reluctant import of command-tab based on its popularity on Windows and as the freeware LiteSwitch.
One common feature among app-switching methods is showing which applications are currently running. On iOS, this distinction isn't made; I argued that it should be, as it would benefit novices and experts alike. On the Mac, only running apps show in the command-tab switcher, with a single and recent asterisk: an app available for Handoff will appear on the far left, before the frontmost app. And although Apple has threatened to kill it several times, there's a system preference that controls whether a dot appears next to running applications in the Dock.
I rely on those dots, especially when managing memory usage on my MacBook Air, which only has 4GB of RAM (it's my work machine — the configuration wasn't up to me). But I have to be careful about trusting them too much, especially after a restart. System-wide restoration of open apps and windows is a great feature in OS X, but it makes the Dock dots lie. If an app was running but with no open windows, after restart it will show as running, but the app doesn't relaunch in any way. You won't find it in Activity Monitor or, indeed, in the command-tab switcher. It saves RAM, which is great until you realize that you haven't received any emails for hours because your "running" email client actually wasn't.
I understand the desire to simplify by ignoring the status of apps, especially in a world where cold app launches can often be measured in milliseconds; then low RAM ceilings only restrict simultaneous use of apps. But aggressive killing of apps (either by the user or the OS) may affect the ability to check for updated information or receive notifications. Perhaps someday we'll have no need to care what apps are running. Until then, clear and accurate app switching interfaces are necessary, and that means both the Mac OS and iOS switchers need continued attention.