It looks like Twitter has rethought the change it made on yesterday that affected the way @replies were shown to users. They have now gone back to the old way of doing things…sort of.
So now any tweets that atre started with the @username, and here’s the catch, that are not specifically created by using a reply button, will be seen by all your friends and their followers. Now this makes me wonder how much has really changed. Presumably most replies are done with a reply to button. And if you use the web interface then starting your post with @username will automatically get turned into a reply as if a button were used. I don’t know how this affect TweetDeck and other third party clients but time will tell.