This subject is probably on many websites and blogs considering the massive number of them during this, and pretty much every, election. I don't know about you but attacking your opponent or the issues will not influence my vote. In truth commercials have very little influence on me in the first place. This is especially true since I do not watch a lot of television - I prefer to watch shows on DVD and get my news from the internet.
If the ads are truthful than they would be good, since they would be spreading knowledge, but a large number of them are falsehoods, exaggerations, or misleading half truths. That so many of them are shown is very annoying but what bothers me the most about them is that they will influence people votes using false information. I make an attempt to look up candidates/issues before I vote, get the actual facts but many people do not. They make their choice based on party, ads, or because people they know are voting one particular way.
There are several sites that fact check the various claims made during ads/interviews and people should check them out, not take what they see on tv as fact. Of course these sites are not perfect either but are much more accurate than the ads.
Washington Post Fact Checker
Urban Legends Reference Page - Snopes Also tells about urban legends.
Also should check Fox Attacks.com because even though Fox News claims to be fair and balanced they are not, they lean far to the right.
In Japan there are attack ads as well, though not as many political ones. The reason for this is because Japan has a one party system. The Liberal Democratic Party has been in charge from 1955-1993, 1996-Present. Not all attack ads are political. There are other types of attack ads as well.