[Cross-posted from my Posterous blog]
This is my preferred way of using Twitter for Mac.
Firstly, click on the stream you wish to view, e.g.: @replies, a list you have created or a hashtag you wish to follow. Then click Shift+Cmd+T and it will open that stream in a separate window. Do this for each stream you wish to follow.
Today I have my ‘Niche’ list open in one window and my @replies in another. The main, Twitter for Mac, window is minimised to my hidden dock.
Desktop background is by John Carey.