I have been working with the Objective-C UIWebView object and have found a few interesting items.

UIWebView is how an Objective-C programmer can include web data in their application.  This UIWebView class uses the WebKit engine to handle all HTML, CSS, and JavaScript in the data that it is sent.

Unfortunately there are a few items that are missing in the current beta (5).  For example, the opendatabase JavaScript function always returns null in the UIWebView as apposed to working correctly in the current pre-release Safari and Mobile Safari applications.  Apparently this has to do with the programmer not being able to indicate a quota for the database, the default being zero.  When a database has a quota of zero it will not be written to disk and therefore the function returns null.  This also appears to be true if you use WebKit to develop an application on your own as well.

I have filed a defect for this missing behavior.

I also have not yet seen any ability to use the CSS Transitions, Animations, etc. in any of the betas so far.  Hopefully this will be rectified soon so we can see what the performance of these items is like on the iPhone.  The seem to work quite well in the pre-release versions of Safari.