Now that the thread has been brought back from a 2 year coma... I'll chime in :)
I'm currently wearing my Mudman, so I can't say anything too bad about G-Shocks. That being said, I wouldn't think of wearing most G-Shocks with a suit; postur pulls it off pretty well, but that's a very tame G-Shock with a handsome (and very muted) color scheme. I wouldn't judge anybody if they were to wear a G-Shock with a suit, but then I wouldn't judge someone for wearing Crocs or flip-flops with a suit; it's just something I'd never do.
Some say that you should do what you want screw what people think. To a certain extent that is true, but also realize that some occasions call for different attire; my friend just got married and I wore cap-toe balmorals and a slim black Orient dress watch, not Crocs and a red G-Shock. I guess the moral is just because you can do something doesn't mean you should... but honestly these "should i wear..." threads are all just matters of opinion anyway and in the end it never really matters for much. Ultimately we all have a public image; it's why we don't wear fried eggs for hats or dye our armpit hair. We could, but we don't. (well I do, but don't tell anybody). So if you're asking whether or not it's a good idea to wear a G-Shock 24/7, for any occasion, I'd say it can be done but there are more stylish options out there.