If I had to choose one theme of Twitter messages as my least favorite, it would be messages that provide no context to me as a reader. They're generally messages that are relevant to the sender and only one of the sender's followers yet were sent publicly rather than as a direct tweet (or any of the many other forms of communication available for 2-way communication).
Here are three examples:
@reply Thank you.
@reply Agreed.
@reply Indeed.
The messages are positive. However, they're also irrelevant to almost all of the sender's followers.
Consider adding a little context to @reply messages so all followers can be part of the conversation.
Book of the Month: New Rules of Marketing and PR - David's Reading of the Audio version is excellent
Gadget of the Month: Canon SD880IS Digital Camera
Web Site of the Month: Google Docs - Used to Write Technology Evangelist Posts