Remember that the next iteration of Mac OS—Lion—is about bringing some innovations from iOS . Apps on the Mac should and will continue to feel Mac-like, but it makes good sense for them to become more iOS-like, too. My two-year-old is an expert iPad and iPhone user, and has been for six months.

Modern touchscreen interfaces—on iOS devices and their competitors—often tend to rely on drilldown mechanisms for navigation. There's a feeling of tapping down into an app—whether navigating mailboxes in Mail, or RSS feeds in or . On iOS, and especially on the iPhone, such navigation is seemingly necessary because of the limited screen real estate.

Twitter for Mac has the advantage of your (comparatively) enormous monitor, and yet it too employs a drilldown-style interface. That interface, coupled with smooth and subtle animations, helps you keep track of where you are in the app—precisely the way the app works on your iOS device. It doesn't need to do that, but I believe Twitter correctly concluded that the approach offers mental navigation benefits, in addition to space-saving ones.

Twitter for Mac isn’t perfect. I miss features from each Twitter client I leave behind. But more than anything, the app feels like the future. Not the 2030 future—the late 2011 future.