I not think it is the issue if it is looking professional or not just because of some ads. with Freefind you even can have some version without these ads. The Free version can also be integrated into your site.
Point of the original post here was that it is about a linking strategy and at the end the only one who is real linking is you (the user of this service).
Nowadays we see a lot of mixed ideas about a website and the way to use 'tools'to spice it up. I also tried to use this free service and till now there are NO ads at all. The only ones are on top of the results page by text links to other sites. It is like the SE's are doing too with the sponsored links on top of the 1# result page.
There are different kind of sites with the same budgets and if you can bring some extra to a site by using such tool it cannot harm at all, as long as the look of the site will be the same.
The result pages are not for any ranking at all and also database driven. No effect on the ranking too because it is not pointing to a page and this page is as some smell. After clicking away it is gone.
Again it is IMO not affecting YOUR page rank but it is a one way ticket for that to Freeserve.
The million dollar linking strategy will be the secret of the one who discovered it