> I was looking at Google Webmaster tools, and that's the metric they are using there.
this is still a strange metric, measuring rather google-visibility than business of the server.
When one compares openacs (with db access etc.) with a server delivering cached pages, one is comparing the computation of pages on the fly and their delivery with the pure delivery of precomputed pages. But that's not comparing aolserver with the caching proxy, but the OpenACS application vs. the proxy. Actually, for dynamic pages, the caching proxy can't do much unless it is skipping cache validation (which would lead to incorrect deliveries, no user tracking etc.).
> I've never seen XoWiki pages to come out faster then 250ms on any (Intel) hardware
Well, on openacs.org with Ubuntu 10.04.4 LTS + pg835 (intel server), i see on such a test 0.101secs real time, and this is with general comments and various includelets in the side-bar.
time wget http://openacs.org/xowiki/aolserver-install
The total average on openacs.org is 176ms over the last week. One should note that openacs.org is not a tuned site and it is running still a quite old version of OpenACS.
Maybe i'll get in touch when it is less busy on my side to figure out, what makes your site slow ...
all the best