Hi — great discussion. Thanks for giving mod_pagespeed a shot. We are trying to improve it based on this early feedback. In particular, please try our latest update to fix the high server load and general stability issues.

A few answers to questions raised in this article and the comments follow:

We will add support for WP Super Cache — it’s delivering gzipped HTML to downstream filters without marking it as gzipped. In the meantime, many users have pointed out the workaround of turning compression off in WP Super Cache. We added that to the FAQ. We believe mod_pagespeed complements the functionality of WP Super Cache and would like to interoperate better.

Donncha is correct; our doc has a bug in it; now reported as Issue 52.

All resource transformations, such as image compression and minification, are cached by mod_pagespeed so that the Apache server doesn’t have to recompute them on every page view. Server load can still be improved however, and we will be working on that in the coming weeks.

I’m not sure how mod_pagespeed could break file associations (cgi php etc). Perhaps you could send your .conf file(s)?

mod_pagespeed does not perform black magic. It automates the best practices, some of which are cumbersome to execute manually.