Here is a problem with jQueryMobile form parts rendering on WinPhone 7.0 platform.
Right now we are implementing support for WP7 in Rhodes framework. To render jQueryMobile-based UI on WP7 platform we are using WebBrowser control. There are some rumors that this control is based on SilverLight version of control.
But the problem is in the rendering behavior of WebBrowser control. It differs very much from rendering behavior of standalone web browser application (IE Mobile I guess) in WP7.
As you can see it definitely has a problem. So I unsure that WP7 platform support may be considered as "A-grade". I guess we aren't alone with this problem, PhoneGap may have this problem too.
If it helps we may provide you sample WP7 application code with WebBrowser control so you will be able to fix the issue.