Good news, new iPad users: everyone’s favorite iPad news magazine Flipboard (OK, my favorite, but I hear the Flipboard / Zite battles get fierce) is now Retina-ready. I know, we all thought the enhanced app would be approved by tonight, but, as it turns out, the update was shipped a bit earlier. Consider this your PSA.

However, in the brief note Flipboard sent me about the update, something struck me as interesting: company co-founder Evan Doll casually speculated that the Retina Display would lead to longer Flipboard reading sessions. Will that actually be true, though, in the long-term?

Of course, you already know everything about how excellent the new iPad’s display is (like putting on glasses for the first time), so you can imagine how nice Flipboard will look, given its emphasis on big pictures, and a glossy magazine-like appearance. The company says the update will make the images more saturated and sharper, and the typography more comfortable to read.

But it wasn’t until I read Doll’s statement – you know, “blah blah blah, Flipboard is amazing…Retina’s so awesome…blah blah, we believe people will spend even more time reading their Flipboard,“  that I realized something: we don’t at all know that to be true. The world has never had a tablet with a display like this and the long-term impacts on user behavior are still unknown. It’s possible – I’d say, it’s even likely – that a beautiful display like this will cause changes in user behavior. But how much? In what way? And in which app verticals?

It’s funny, but this particular side effect of the iPad Retina rollout hadn’t crossed my mind until just now. If anything, I’ve thought of the Retina Display as a merely selling point, one of the many reasons to upgrade from the older model iPads to the new one, just as it was one of many reasons to upgrade from older iPhones to the Retina-ready iPhone 4.

But Retina Displays impacting users’ time spent in-app? That would be interesting, if it turns out to be true after the initial ooh-and-aahness of the new iPad’s display wears off. Plus, you can’t correlate the impacts the Retina Display had on iPhone apps as to how the change will impact iPad. The devices, while both mobile, are used in very different ways. The iPad is designed for immersive, lean-back consumption experiences, so display improvements could lead to increased app usage, I suppose.

But this question really boils down to how much of an app’s usage is based on the content versus the presentation of that content?

This is an area that’s only now really being explored in any detail. Case in point: Fab.com found out just a few weeks ago, how incredibly different the behavior of its iPad user base was from its mobile and web users. They buy more, shop more often and are on track to account for 25% of the company’s revenue over the next two years. But what Fab still has to speculate about, is why. Like most everything in the world, there’s no one simple explanation for the matter.

But with the launch of the iPad’s Retina Display, there is a possibility of homing in on one area of user behavior: before Retina, and after. Let’s see what happens.

The Retina Display’s impact on the app usage is a metric I’d like to follow up on in a few weeks/months/years’ time. Hopefully, Flipboard will be open to sharing that data. In addition, feel free to send me your metrics, Retina-ready app makers, if you happen to notice any Retina-induced changes to user behavior. I’m @sarahintampa on Twitter. Contact info on my profile.