"good luck with that" 

This shows that courtesy is not dead. It's a very elegant urban code for, "I DONT CARE" but more accurately,"I REALLY DON'T GIVE A FLYING FUCK".
In some communities it means "YEAH, LIKE THAT'S GOING TO HAPPEN". So if something actually does happen you can never be called out and say it never happen.

expl.Friend 1. I would like to study computers. There is good money in it and you dont have to work so hard.

Friend 2.You aren't logic minded enough to study computers,"good luck with that"!

"good luck with that" by Urban Dictionary November 11, 2006

Good Luck With That 

Phrase where you don't really care what happens, you're just glad it's not you who has to do the said person's task.

DUDE 1: My Mom wants me to go on a diet where I have to eat only lemons and cabbage and drink only prune juice.
DUDE 2: Good luck with that. (Thinking: Haha! Loser!)

Good Luck With That by Jim E. Junk May 13, 2006

good luck with that... yeah 

This is a common sarcastic response to any exclamation of enthusiasm or joyous anticipation. It's intention is to present your general disinterest
or disliking for their suggestion.

Infact it could be said that the "yeah" actually means "no". This is evident by the highly sarcastic tone in which it should be spoken.

"I'm going to go and love up random people who once said hello to me now"

"Good luck with that, YEAHHHHH"

good luck with that... yeah by morgangills February 26, 2005