Just remember, you only get paid when someone clicks the link, THEN clicks a paid link in the search results that gets displayed.. i never had much luck with the link-units..
I've found them to get a lower CTR but higher CPC, thats why I continue to use them. They seem to pay more for some reason.
Google just upped the limit of these types of ads too. You used to be allowed to only have one of these on a page, now you can have three link units.