In 1.4, Advanced Search respects the collapse_display field of civicrm_custom_group, i.e. displays the group in an initially collapsed fieldset if collapse_display is set. This behaviour has changed in 1.5: it displays expanded even if collapse_display is set. This makes the search page unwieldy if you have a lot of custom fields & options. (Tested on v1.4 rev6012M, v1.5 rev6646M).