Ask HN: do you use the phrase 'killing it'? If so, WTF does it mean?

yes I use it when I talk about my competitors aka Flickr,43things,and Instagram for the exception of 43things the rest of them are killing it!

I don't use it much, but it means something like "performing really well."

"Those guys are really killing it" is roughly equivalent to:

"Those guys are really ripping it up."

"Those guys are really shredding."

"Those guys are cooking with gas now."

etc.