Repeat notifications are the killer feature for me. This is a small thing, but the option to change the sound of repeat notifications to be different than the initial sound would be helpful.

I'm concentrating on a task and a text comes in. The popup shows it is not important and I get back to work - no loss of concentration. 2 minutes later another alert. I did not see a popup notification. Did I miss it? Is this a repeat alert or did I miss a new text and is that new text important? Now I have to stop and check which derails what I was working on. A different sound for repeats would help this problem.