Here's why I typically don't like In-app purchases, especially with games.
Having received iWork ’09 in bundle with my then-new MacBook Pro back in 2009, I wasn't sure of my eligibility for a free iWork ’13 update. The Mac App Store app suggested I wasn't. It was a little bug, instead.
Great article by Jason Brennan, reflecting on how overlooked the stylus is as interaction tool and input device, with insightful contributions from various developers.