Of course, that's not really a fair comparison, as the iOS version sprung onto the scene as an unknown quantity. At the same time, demand for an Android version had been pent-up for months, and had been ready to explode.
Android owners were anxious, very anxious, for a version for Google's mobile platform, and once Instagram launched a pre-registration process on March 24, there were a flood of sign-ups. Instagram attracted some 430,000 signups in the days following the pre-registration launch.
Instagram is, if you haven't already downloaded it, the hit photo sharing app that allows users to share on Facebook, Twitter, Tumblr, Foursquare, and Flickr (coming very soon to Android).
With 5 million users already and still rising, we'd have to say, "Get used to it, they're not going away."