It's nice to have one part of my life where I don't have to figure out who to ask for a refund if things go sideways, wonder how much of a hassle that'll be, and don't even have to think about whether a transaction is reasonably safe. Do I want that to be my entire life? No. But I'm very, very happy not to have to wade through a shady bazaar to pay for commercial software on my phone and tablet. I've got enough stress navigating private bureaucracy in the entire rest of my life. Having one that's very simple is nice. I don't want it to get less simple.
I benefit from competition between app providers in a variety of ways on the App Store, just not competition on payment methods. That competition is provided by Android—if that weren't around, and thriving, I'd worry a lot more about Apple's mandating a payment method on iOS. As it is, as a user, it's pretty much purely a benefit to me.
