Thanks for the idea frequent. It seems that they have temporarily disabled new requests for the time being on the jqm github :( all I'm able to do is file issues. Hopefully they will reopen the request section after 1.0 is released.
- never mind, I saw that I could post the request under issues, so I did :)
I made a final performance test yesterday, I made two test pages containing every possible element from the jqm docs, one with no enhancement markups and one with the markup allready applied. For the 'vanilla' page I simply used the jquery mobile rc1 compressed script and for the pre-enhanced I used my own heavilly modified. the difference was about 1.5 seconds in load time on an iPhone 4. Every resource was loaded from the server and the both used the same css ( took about 5 seconds for the pre-enhanced and about 6.5 for the non-enhanced file over a 3G mobile connection).
I'll admit that the test page was not replicating any real world scenarios with so many elements, but there clearly is a significant speedup of page rendering if you disable the markup enhancements through the js.
The drawback is that you end up with much larger html documents (mine was 19KB - non-enhanced and 36KB - pre-enhanced). And even though reducing the data might be perferable in many cases I think the option to allow for pre-enhanced pages might be good when speed and load times are a big issue.