"Android is not in my world. It's not in my attention span most days. Thinking about the iOS app is a full-time job, and staying competitive on iOS is a full-time job." This quote comes from Instapaper creator Marco Arment not even three weeks ago in an interview with Joshua Topolsky on On The Verge.

Evidently, Arment was keeping a pretty big secret. Instapaper for Android launches today for $2.99 on smartphones and tablets, and you can find it in the Google Play Store and soon in the Amazon App Store and Nook Store. What makes the app launch so significant is that aside from Instagram and Flipboard, Instapaper might just be the next-most-desired (and elusive) Android app ever. The excitement surrounding a possible Instapaper Android app has not been just because people wanted the app itself, but also because creator Arment often publicly expressed distaste for building on Android — almost out of principle. "I think it was the success of the Kindle Fire and the Nook that tipped my hand," Arment told us.

So, he entrusted the Instapaper name to developer Mobelux, which has previously built Tumblr for iPhone and Android, as well as Carousel, a handsome Instagram viewer for Mac. Mobelux wasn't the winner of the app-building challenge Arment started in jest, but was instead a great fit with a compatible heritage. Arment met Mobelux co-founder and Creative Director Jeff Rock all the way back in 2008 when Tumblr was in talks to buy Rock's Tumblrette Tumblr client for iPhone. Arment (still full-time at Tumblr) got to know Rock and his team, who quickly became the backbone of Tumblr's mobile app strategy.

After Arment's scuffle online over the fiscal viability of building an Android app (and several years of hanging out with Mobelux at WWDC), he approached Rock and asked if he was interested in building an app for him. "[It] seemed like a perfect project to collaborate on," Rock told me, so Instapaper for Android was born, a bit longer ago than you might think. But is the app any good? Read on to find out.