here are updated copies of the webassist/themes/theme_open.php and
webassist/themes/Default/images/installed.jpg files that should help speed things up.
also included is a ps4_indexes.sql script that will create indexes for the Power Store tables. for details on how to run the sql file, seer the "How to import a MySQL (.SQL) file to your database" tutorial on the learning resources page:
one thing that can effect performance in power store is product options. when entering product options, make sure to use the correct option type. For the most part, simple options should be used. Only use advanced options if the option should effect the product price or you would like to change the description.