Channel01 - 12:30 am on Feb 11, 2011 (gmt 0)
It may be worth generating a search query report and seeing if any of your keywords are matching to queries which are irrelevant or unqualified. Negativing those queries out will improve your CTR and thus your ads' QS.
This is definitely a good suggestion for general account maintenance but it won't improve QS. Google has stated that they only judge QS based off of exact matches of the keywords that are bid on.