Are you using caching plugins? These are usually help. Currently, I'm using W3 Total Cache (link)
As far as issues go, it can be a number of things:
* your theme coding
* your database
* plugins that may or may not be compatible with the version of Wordpress you are using
* plugins that may or may not be compatible with other plugins that you use.
As far as Dreamhost and Wordpress go, there is no such thing as "compatability" issues. Dreamhost is a php CMS that communicates and stores data on a MYSQL database.
More information on your problem would be helpful as, as I mentioned earlier, it could be a number of things that are causing you problems.