The value of such of tool though points to one of the reasons why web technologies will ultimately prevail over native for most applications -- ease of use.
I hope to see the day that given the right development attention one can make a web app that feels fast like a native app. It might already be possible for some kinds of apps.
There are apps popping up that are really an ember or angular one pager wrapped in a native shell.
HTML/CSS on Webkit gives you an amazing layout engine for free. Building UI for native apps feels like "web coding like it's 1999" with a lot of absolute positioning and use of sprited images. I wonder if things improved in iOS7.
That's an iOS issue, not one inherent with native apps. Android/Qt/Windows Phone/literally any other toolkit provide flexible layouts which are much more powerful and often easier to use than CSS. And if you need a custom layout, you can actually write a new layout manager which is just as fast or faster than the built in ones, no javascript to set absolute positions on everything.
> why web technologies will ultimately prevail over native for most applications
All your users care about is UX and features. Native sdks provide more features than web apis, are more powerfull and your users feel the difference. Native sdks are not going away anytime soon.
While I don't think that native SDKs are going away any time soon, there are huge classes of applications where those additional features aren't needed, and even more that can us in between solutions like phonegap. I think that very few applications outside of games really need features that a web-based UI can't provide on modern mobile devices.
Didn't Facebook famously switch from HTML5 to Native for their iOS app? If a company with the resources of Facebook can't do it effectively, I think you underestimate the problem or overestimate web-tech capabilities.
The value of such of tool though points to one of the reasons why web technologies will ultimately prevail over native for most applications -- ease of use.