To expand on this, CSS totally supports the basic performance of styling native apps provided you use features with the ergonomics of styling native apps (i.e.

To expand on this, CSS totally supports the basic performance of styling native apps provided you use features with the ergonomics of styling native apps (i.e. inline styles). It's when one wants to be able to better declare what the styles will be that you have performance implications, and as pcwalton says these are worse for native styling frameworks since they don't have much optimization work put into them. (Also, wrt the original comment, all this font-size handling isn't particularly a perf issue. There are other minor font perf issues, but this isn't one)