Open this URL on your phone to see: http://dev.sencha.com/deploy/touch/examples/production/index...

My impression- there is still a huge different in the "feeling" of a native app v. a Sencha app. As a "mobile first" developer, I wouldn't dream of using Sencha.

The good news for Sencha is that many companies will prioritize cost/platform reach and a "good enough" experience will be, well, good enough.

At least on Android, it "feels" fast enough. However, it breaks navigation when you use the Back button (in the interface) and the Back button (part of Android).

This alone, makes the app clunky.

If you are getting a two-second lag on something it is because you are building an application that is blocking on remote assets, not because you are rendering using HTML; there are many native applications on the iPhone (including ones from Apple) that have two-second delays when you click things, and it is because they are pulling information from some API, such as YouTube, to render the content.

As for "feeling", however, there are a ton of little things that are broken: the blue touch highlight sometimes clears and sometimes doesn't (seemingly dependent on the target of the link, not the source), they are doing some silly HTML5 pushState mechanism to mess with the back button incorrectly (specifically, pushing a new state when you go "back" in the UI when that should really pop a state), etc..

The thing that is really freaking me out is that I'm having a hard time figuring out if they are using native scrolling or not (as in, on iOS 5.0, you can just say "this div is scrollable", and not have to re-implement the behavior): the curve seems wrong and glitchy, but they have nailed enough of the actual visual elements that it is no longer obvious to me that it isn't just that they figured out a way to make the native scrolling perform poorly. ;P

In my experience, performance on iOS is fantastic, while Android lags behind a small amount. Sencha isn't quite at the Native speed level yet, although it's certainly close.

Well just remember, you're building your homes inside the browsers, the day Android fucks up or the day apple announces a radical change to their browsers, it might affect everyone. Well for all good reasons everyone has an incentive to improve their browsers so far.

Performance on iOS is superb. Performance on Android is workable - I test regularly on Desire HD and Galaxy S2. Without animations android performance is really usable, even in a heavy app like mine (shit loads of decorations, 3k js)

Of course it doesn't have a lag. You can't actually differentiate a native and a sencha app.

Their kitchen sink demo is really slow on my Touchpad with CM9 alpha0.6.