[davidu]

I'm pretty sure it doesn't work that way. I think everyone see's your @reply -- perhaps you mean DMs?

[icey]

jsb is correct; they made this change a few months back.

[shaddi]

Extra tidbit: this is the reason for those ". @foo ..." tweets you may be seeing. If any character precedes the @, then the tweet will appear in all your follower's feeds; otherwise, it behave as jsb described.