I remember back when i was a kid in the 90's, dungarees were a huge part of my wardrobe... they were super easy to throw on and they were super popular with all of my friends. Now in 2010, they're back and i'm not sure if i have the same love for them as i used to. I admit this trend is definitely not for everyone, and its especially not for those who work for high-up-there companies. Its a kind of laid back look that doesn't require much effort, and maybe thats the point of it, but if you don't want to look like you just stepped out of the pig pen i suggest you go for dungarees that are a solid color and have shorts instead of the long denim jeans. Personally I think it gives you a more put together look and a not so .. sloppy one.
I would never really wear denim overalls, the closest that i'm ever going to get is my denim romper.