I guess I'm in a lucky position. I am No. 1 in google seach for the keyword I am targetting and I also have the No. 1 ad for the keyword on adwords. So when the search is processed I get both the No. 1 search ranking and the top on adwords. Since i can't track conversions with adwords (I can't track search referrals either!) I wonder if it's redundant to keep the ad? It costs miminal to have it run at the moment, but I guess it would be one less thing to monitor. Wonder if anyone else has been in a similar situation...
What is your objective from the ad? Are you selling something or its just for branding. In both cases you should keep running your ad.
Simply because your add includes the call to action, is highlighted, and links to the exact landingpage of your choice should be few of the good reasons to keep the add imho...
If it doesn't cost that much as you are saying.. then keep it.. But if it kills from your time.. then that's a different story.