QuickReply for SMS functions basically as an expanded plug-in to the built-in SMS app. There is no icon for QuickReply and it just interacts with built-in functionality. QuickReply attempts to solve a lot of the problems that the native SMS app still has. The major one being when you get a text, you have two options, either close the text or view it to respond. If you're in the middle of doing something on your phone, it'll close you out of it in order to take you to the text app.
QuickReply solves this problem by adding another button. In addition to the traditional close and view buttons, you'll see a reply button to the right. When you click reply, it'll simply bring up a keyboard and you can reply to the text without interrupting the app you are currently running. When you're done, tap send and you're done! The keyboard disappears and your text sends in the background. In settings, you have the option of changing the traditional keyboard to a transparent type keyboard if you'd like as well. You'll also see an option to replace the view button with a call button.
With the latest update to QuickReply, contact pictures were added. I thought this was a really neat addition. If you have a picture set for a person in your address book, it'll pop up in the right hand top corner of the text on the homescreen. Speaking of the homescreen, QuickReply also allows you to reply directly from the homescreen. Enabling the lockscreen option in settings will allow you to double-tap a text off the homescreen and bring up a keyboard to respond without even having to unlock your phone.
QuickReply is definitely one of those apps I'd sorely miss on a stock iPhone. For anyone who's jailbroken, it's definitely worth the $2.99. And if you'd like to try it out, they have a trial period available.
[$2.99 - Cydia Link]