I just fixed the assessment portlet and had a quick look at other portlets (forums and news) and the queries used there are sending shivers down my spine: for every row, acs_object.name, apm_package.parent_id and site_node.url are used which themselves are doing at least one select!!! For performance reasons we should really consider fixing these queries because the information gotten in this twisted way can be fetched from the site-nodes cache or selected in a really easy way by joining the appropriate tables.
Second, if somebody touches the portlets anyway, they should be rewritten to use the listbuilder, i think.