[mirimir]

Not a Twitter user here, but would this delete retweets by others of your tweets?

Those might include tweets that you'd most want to delete. As well as ones that you'd most want to retain, for that matter.

[jamiehall]

Yes, it takes care of that; if someone has retweeted you with a comment, the thing they're commenting on is replaced with "This tweet is no longer available." (Obviously, it's no defence against people screenshotting your tweet, manually copy-pasting what you said, etc etc.)