As far as Apple is concerned they already did implement a quick reply function:
Reply from Lockscreen
Reply from Notification Banner
Reply from Notification Center
I don't think you understand what the Quick Reply feature does.
None of those are "quick reply" features. All they serve as are shortcuts that take you to the Messages app. I don't want that.
Quick Reply consists entirely of viewing and replying to a message all in a single pop-up box, OVER TOP of whatever app you're currently in. So you see the message, reply to it (or close, ignore, whatever), the box goes away, and your app never left the screen.
The way stock iOS 5 works, it completely leaves the app you were in, and goes to the Messages app. Once you're done replying, you have to leave the Messages app and manually switch back to the app you were working with. Personally I can't stand that... it's sort of a pain.
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Really? Mind telling me where mine is at on my JB phone? Oh that's right I don't have it on my JB phone. Do not assume just because it was the first thing you installed.
Their are thousands of iPhone users out there. Just because a little group here wants it means nothing to the other crap load of iPhone users. I personally never liked BiteSMS or another messaging app that had QuickReply. I'll reply when I am ready to reply back. And I mean it is so hard to just go into the messaging app to reply back to something really quick.
Quick Reply is not mandatory, lol. Calm down buddy. It's just a pop-up, just like the one you get on iOS 5 anyway. If you don't want to reply, ignore/dismiss it.
And yes, switching to the Messaging app, replying, and switching back to your other app is much more tedious than not having to do it at all.
Some people have the silliest arguments.
"OMG, NO MORE OPTIONS PLZ!!!!!!!!!!!!!"
Give me a break.