I would point out that WKWebView in iOS 8 provides full Nitro support, so that's no longer an issue. I'm not sure if browsers are using this yet, though – there was some talk about difficulties with certain features.
Pretty active development. No releases on the app store, though.
In my project, I implemented a small component in Swift, and was a pain to convert. The automatic source upgrade tool did a terrible job, doing more damage than good.