I checked this out after seeing it on Hacker News, and the demos that I tested out are very impressive. I've been using jQuery Mobile, and this framework appears to be much more responsive and generally a more attractive UI.
There also is an IDE specifically for Mobello called Mobello Studio. I downloaded it (you have to enter your email and it sends you a link) and, based on the 30 minutes or so that I played with it, seems to be very good.
It appears to be an extensively developed framework (the API documentation has a massive list of functions), and the various widgets/components mostly worked very well on my Samsung Galaxy II Skyrocket (except the datepicker, anybody wanna try it on an iPhone?).
My initial impression is that it's a very good framework and appears to be far ahead of the ones that I've tried out so far, but I have a couple of hang ups...
-I don't know anyone using it, and there is practically zero coverage of it online at the moment. A search for "Mobello" on Stackoverflow yields zero results.
-Most of the documentation is in Korean (Google translator in Chrome mostly fixes this).
But wow, it works so well
on my phone and looks really, really good. Has anyone used Mobello or done anything with it?