As explained in other answers it literally means "in my opinion". The phrase is most often used as a starter when someone wants to give another one some advice, or is making a comment on another.

However I'd add that it conveys a sense of intimacy and sincerity, so it's more likely to pop up in the dialog between two close friends. Or it could show up when someone senior (or of higher social status) is giving advice to a junior that they care about.

Thus this phrase sounds impolite in a formal or professional setting, or between two people that are not so familiar. It's probably rude for a junior to say "我看你呀" to a senior especially in the East Asia culture, unless they're really close.

In this regard, I think the phrase is actually best translated as: 

_Bro/Man/Kid, I think you should..._

我看你呀，还是早点儿洗洗睡吧. Bro, I think you should just leave it.

我看你呀, 有个工作就去干吧, 不要挑三拣四了. Oh man, just take the job, don't be so picky.

我看你呀，将来是个大人物. Kid, you're gonna be somebody.