After calling for applicants to try out its beta testing app back in January, Twitter has now released its new 'Twttr' test app, which includes a completely new layout for tweet replies - and has immediately sparked mixed responses from users.

As you can see above, the new tweet reply layout helps to maintain the specific flow of tweet threads. Tweet replies are indented directly below each specific tweet within the stream, while replies from the original tweeter are highlighted with a color line along the left side of the response.
Most testers seem pretty positive about the changes, saying that it makes it easier to follow the conversation, and reply to specific elements. Some have criticized the 'chunky blocks' and how they look, while others have noted that the layout can become difficult to follow if/when the thread gets long. But overall, the test, thus far, seems to have merit.
Twitter first announced that it was looking to re-design the tweet reply process last September, when it showcased a very different looking color-coded reply system.

The version released in the Twttr app scales back the color coding, but uses largely the same process, with threads and replies that are more reminiscent of Reddit - though without the repeated indentation for each subsequent response.
This is the first of several features likely to be tested in the Twttr app. Twitter has also detailed 'ice breakers', which would be used to spark conversations with people on the platform, and status updates, which would essentially negate the need for people to put things like 'Andrew Hutchinson at #SXSW' into their Twitter handle.
The Twttr app icon itself has also had an overhaul already, switching from a diagram of the Twitter bird to just a plain, light blue panel.
As explained by Twitter co-founder Biz Stone:
Notice our new prototype? @jack and I named and designed it based on old times. It’s called, “twttr." The bird flew away from the app icon representing: Simplicity. Blue sky thinking. We’re re-working. Not there yet; hence, no logo. Bold and a little weird. #LetsHaveAConvo pic.twitter.com/WaNR2mOXO9
— Biz Stone (@biz) March 11, 2019
At present, only a small group of users have access to the Twttr app, but Twitter has encouraged those users to share what they find using the #LetsHaveAConvo hashtag. So if you're interested, you can tune in to that hashtag stream to get some insight into what people have found.
It'll be interesting to see what users think of each new addition, and how that relates to subsequent roll-outs and updates. Through this, and other processes, Twitter's trying to be more open to its community, and to share in its evolution using more collaborative, transparent means. Whether that'll work out or not will depend on how Twitter uses such feedback - and given this, you'd expect that anything that does get rolled out to the Twttr app will actually already be pretty close to launch, that this will be the final logic check before wider release.
So, expect an update to your Twitter replies soon - and if you want to get a head start, stay in touch with the #LetsHaveAConvo tag.