The only issues I've had so far is the full page ads popping up more than once every 24 hours. I'll see two or three in a half hour. One of the banner ads also started screaming at me which is really quite obnoxious. I haven't had any problems with viruses, though.
If the full page ads can actually be cut down to one every 24 hours then I really wouldn't mind seeing them if it helps the site.