jQuery Mobile is my preferred choice for mobile development.
Having used standard jQuery for so long, i appreciate how this product will consistently been improved and updated upon.
Mobile frameworks will need to keep inline with new phone devices which appear all the time and the jQuery team should be able to accomplish this best. The framework already covers the key devices that i would consider necessary to support.
At Rated People i created, in just a fortnight, a fully functioning mobile web app ready for user testing. The spec was easy to use and offered enough flexibility to create a standard mobile site with ease, allowing the user testing to proceed earlier than had been anticipated.
The final completed product used much of my code from this initial prototype and the time saved at that stage ensured that an extra stage of testing was possible, ensuring a better final product delivered in the same amount of time.