I watch a lot of my anime dubbed, which can have some good things and some bad things.
One of my favorite things about dubs is that I can focus less on what the characters are saying and more on how they say it. When I first was watching the Melancoly of Haruhi Suzumiya, I watched episode 00 subbed and thought that it was dumb and stopped watching. However when I watched the dubbed version of that episode, I was able to understand that it was a shitty film more because I could focus on how the characters sounded, and how crappy their acting was, and it made me laugh like a madman. (On a side note I would recommend that you start on episode 01 for Haruhi, because I think that episode 00 is something you wouldn't really understand until after you've watched all the other episodes. When I watched episode 00 first, I thought that Yuki was just simply reading the lines without any emotion, but then I found out that was how she talked in the series too). Also I feel that dubs help me put more of a sense of life into the characters. When the characters are speaking in English, I can understand more of the subtle emotions in it, which I can have a hard time decifering when I'm reading subtitles and listening to the Japanese voice actors at the same time.
Some things that I dislike about dubs is that they sometimes have a tendency to try and change the music. Most dubs are good about this like Genshiken, which kept all of the songs in the original Japanese, but others like Ouran High School Host Club, which changed the opening theme song to english lyrics. Although my annoyance with this is not limited to the opening and closing music. If there is music in the anime, I want it to remain in Japanese, which was one flaw with the Haruhi Dub, when they gave english lyrics to the two songs that Haruhi sings during the schools cultural festival. Another thing that I dislike is when an anime dub changes the lines drastically to "Americanize" them or to make them more or less "edgy". "Americanize" is a complete insult to the creators of the anime, because its basically saying that we rather not learn about your culture, so we are going to substitute our own. Changing the lines in general is insulting because it also says that the dubbing company thinks that the story is not good so they will change it as they see fit. I heard that Love Hina's dub is a culprit of this by changing the lines to less "edgy" things. I think that a dubbing company's only job is to translate the original, and give the characters English speaking voices.
Well that is my opinion on Dubs, you can form your own opinion, and please tell me what you think, but keep it clean guys.