Whenever one of my friends gets a new iPhone or iPad, the first thing I tell them to do is install Instapaper. I've had Instapaper on every iOS device I've ever owned, and it is without a doubt my favorite app. It's completely changed the way I consume content online, and has consistently improved with every release.
One of Instapaper's primary competitors is Readability, which launched its own iOS app today. Both offer the same basic functionality - they clean up webpages and bookmark articles for later reading. There are differences in their features (Instapaper's are more robust), style (Readability is smoother and more modern), and the strength of their formatting tools (Readability is more consistent). At a glance, has certain advantages over the other. And truthfully, in the ways that matter to me, Readability might even be a little better.
And yet I can't bring myself to make the switch. I've played with Readability, and I like it, but within a couple of hours I was saving to Instapaper again. In fact, I was saving to Instapaper with a greater frequency than I had in weeks, just to give myself the chance to use the app later in the day.
One thing is keeping me with Instapaper: I trust the developer. That's not to say I have anything against the guys at Readability. They've built a great first release. But I've watched Marco Arment improve Instapaper so many times over the last couple of years and seen him pour so much love into it that I can't believe his app won't continue to get better. As for Readability - I just don't know. I don't know what the roadmap is, and because the devs haven't earned my trust, I can't bring myself to buy into it. I've made a pretty big intellectual and emotional investment in Instapaper, and that's not easy to break.
Now think about that in the context of things that aren't priced at "$4.99" and "Free." Think about it in computers, automobiles, banks. When you trust an institution, an idea, a product, competitors don't just have to match it or be a little bit better. They have to be so far beyond what you already love that it's not even a contest. And still it's not always enough.
That's not to say I'll be an Instapaper user forever. Maybe Readability leapfrogs it. Maybe Marco starts to slip. But the point is that while Readability is a great start, it has a long way to go. And it's not alone.