What I don't get is why they keep going down the same path. Their Android application has evolved from a simple webview to many many webviews over the last year and they still haven't gone native. Maybe they're fine with the detriments when compared with the ease of creation?
I can totally relate with your comment. I've found myself converting from web to native as well. Mostly because webkit is still slow for UI operations like resizing elements that require some Javascript to be processed and so on.
The downside of this is that you start to have lots of subclassed objects just for a gradient or slide-up/down animation that you could do with 2 or 3 lines in js or css.
I wish someday simple view design could be done in html/css and leave the logic and core functionality to the native language instead.
You should write a tutorial on doing such a thing. Especially the part where you bridge Objective-C and JavaScript.
Perhaps I'm mistaken but there isn't much documentation on this online it seems.
Here's a simple JavaScript/native bridge implementation: https://gist.github.com/3688560
It's a great way to launch your MVP, but I've found myself slowly converting pieces to native due to performance issues and other minor quirks.
What the Tumblr folks have now is a great start, but I have a feeling they will make their way down a similar path over time.