Using a solid border for the cursor instead of having it in the text content is a nice touch; because it's separated out you could probably use another animation to get it blinking, too.
Yep, that was my thought, but there might be complications I haven't thought of. This is me guessing without having tried anything.
> couldn't get it to render in a way I was happy with
I might be repeating something you already noticed, but cursors only blink after you stop typing, so if you weren't delaying the effect until after the typing was done that might have contributed.