In my experience, it is rare to find a shared hosting environment that uses a php accelerator which makes a big impact on the speed of an eZ Publish install.
Dreamhost does not offer an accelerator in their php 4.4.4. install. http://php.dreamhosters.com/php4-apache/
They do seem to support compiling your own PHP that you could include this module in with instructions here: http://blog.dreamhosters.com/kbase/index.cgi?area=2538
We ran eZ on another shared host with less than stellar results, but when the site was mostly cached it worked reasonably well.
