When you have send delay on, there should be a "send now" button. For example, when you are having a quick paced casual conversation with a friend you have the option to send instantly instead of waiting 4 seconds in between texts. But when you are texting your boss you still have that 4 second delay where you can still read over your text after you hit send.

I like having it on but it gets annoying when you have to wait a period with someone you talk to daily.

Also, when you quick reply when using "Android heads-up" it sends instantly.