Emails are all well and good, but with many email clients it can be cumbersome to have numerous replies open for different people. Sure, you might not need to reply to absolutely everyone at once but there are people out there who can do so. The one issue with Microsoft Outlook, generally accepted as the standard for most offices, is that replying required an entire window.
Why did it require an entire window? Why couldn't they have just done what other clients were and include a quick reply option within the email area? Whatever their reasoning, Outlook 2013 finally bucks that trend and adds a feature that remains sorely lacking in older versions of Outlook.
The public beta hasn't been too bad, since it meant the quick reply window could be tailored to fit the most common requirements among users. This is where the Customer Experience Improvement Program came in handy, since it allowed Microsoft to identify the most used functions. Guess what they did with those functions afterwards? Yup, that's right, they worked them into a quick reply box.
Outlook 2013, along with the rest of the Office suite, is available in a free public beta from the preview website.
Source: Outlook Blog