I don't think it's worth if you're applying this cycle. If the rest of your application is not stellar/stand-out/strong etc. it could be worth it if you delayed application and applied next cycle - that's a big step, I know, and may not be worth if depending on your experiences/background/etc. I retook a 516/delayed my app and was very happy I did - but to each their own, knowing how strong the rest of their app is.