I have switched back.
At the time my issue with Instapaper was only that it wasn't perfectly suited to the way I was using it.
The problem, for me, is that Instapaper’s ‘one thing’ doesn’t actually fit what I use it for. I do use it to save articles. But I also use it to save links, videos , blog posts with photos, etc. Basically anything I find on the Internet that I want to save, whether to read later or watch later or whatever, I throw into Instapaper and get to it later.
And it is true that Pocket has a lot of functionality. The coolest being watching videos directly in the app. But, to be honest, that proved to be not all that helpful a feature. Usually if I'm saving a video to watch later it's because it's either too long to watch right then or I might want to post it to the site later. In the former case I would probably rather watch it on my television via AirPlay, so it doesn't matter whether its in the Pocket app or in Mobile Safari or whatever. In the latter case, I really just need access to it on my Mac Mini (I KNOW.) because that's where I do video posts (it has to do with how I have TextExpander set up. Long story.). So it kind of doesn't matter at all that Pocket lets me view videos in-app.
What Pocket doesn't have is a really pleasant reading experience. The Instapaper reading experience is just excellent. Beautiful fonts. Customizable font sizes, line height, margins. Really nice dimming to night mode based on the current time. These are features that Read It Later may have eventually added, but the app-for-saving-everything Pocket surely will not. They have no incentive to put that much effort into that part of the app.
And there are little things that Marco Arment puts into Instapaper that make the experience top-notch, whether we as customers notice them or not.
For instance, Marco only very rarely asks Instapaper users to go rate the app. I really can't stand it when an app interrupts what I'm doing with the app to try to solicit a self-serving review. If I weren't such a lazy man I would take the opportunity to give those apps a negative review just for that. (To be completely fair, I can't remember Pocket doing this. I just know that Instapaper doesn't do it often enough for me to notice or get annoyed.)
Instapaper also delays the auto time-out feature so your iPad or iPhone screen doesn't turn off while you're reading a page. As Marco discussed briefly in the latest episode of his podcast this was a lot of programming work for him, but makes the app more enjoyable for people. And that's even if they don't explicitly know about the feature.
Bottom line, the pure experience of using Instapaper is better. And better enough to get me to go though the (admittedly not-very-painful) process of switching back. I was seduced by a neat, 'new' app with a cool video and some neat features. But when the shine wore off I wanted the quality of Instapaper back.