Ira Glass was once asked about how he became a great radio host [1]. His response was that he continued to work on his craft even when he knew it was terrible. Knowing your work is terrible is crucial because it means that you have taste - you know what needs to be done, and you know what would fulfill it, even if you don't have the ability to execute it.
Style is about taste. And note, style is not equivalent to 'dressing up'. Style is knowing what pieces go together to create an aesthetically pleasing form. Style is knowing your body type, your personality, and your needs and putting together outfits that compliment and combine those strengths.
When developers get made fun of for not dressing up, it's not because you're wearing a t-shirt and jeans. It's because you've put no thought into which t-shirt with what jeans. There's no thought about how the pieces fit together. There's no taste.
Taste is critical for us because it's what makes or breaks a product. What makes Apple great? Taste. What let Instagram beat out the plethora of other photo apps? Taste. What allowed Facebook to take over MySpace? Taste. Taste is what will give me confidence that when you are on my team, you will do exactly what is necessary to make us win.
Taste is imperative. Take every chance to show that you have it.
[1] http://kottke.org/11/04/your-taste-is-why-your-own-work-disa...