The author's comment that "Sencha does also come with a Look & Feel, but again, it’s the Sencha Look & Feel, not the Android or iPhone one" is false and also is, imo, a silly reason not to use Sencha. Sencha is entirely themeable and it even comes with iOS and Android themes that you can easily enable.

Sencha does, however, have a steep learning curve. I think thats probably why the author didn't dive into it deep enough to grok the themes.