To preempt a few questions that are bound to pop up: What about jQTouch? While jQTouch is a great framework and we're proud to have it as part of the jQuery community - we really wanted a mobile framework to exist that would truly support all the mobile platforms out there. We chatted with the jQTouch team and there wasn't really any interest on their end to head in that direction. It's obviously going to be a ton of…
While I laud your transparency, I lament the chilling effect this will have on existing libraries like JQTouch. jQuery Mobile isn't available today but this announcement will make a lot of people sit on their hands waiting to see how things play out in the hope that they won't invest in a dead-end platform. Oh well, not saying you shouldn't have chosen this path, just pointing out the consequences...
Honestly, I don't see the "chill" as being a bad thing in this regard: jQTouch and Sencha Touch are doing mobile web development a great disservice by only supporting the latest-and-greatest WebKit platforms. If we can get developers to actually think about supporting more of the mobile platforms that are actually used then I will consider the project to be a victory.
I discuss this much more in our strategy outline: http://jquerymobile.com/strategy/