I have never actually used this feature, and I do not see it in Notepad++. I worry that some people, especially beginners with no experience of this 'feature' would hate this, so it would have to be optional.

Do you literally mean 'parentheses' or also square and curly brackets?  How about quotes? An autocloser here would be useful as Idle would not mishighlight the remainer of the text.

How does it increase speed? Hitting -> to skip over the closer is hardly faster that typing the closer. It might reduce errors though.

Tal, any opinion on this?