Unfortunately it is for many people. Thankfully we have the unfollow button for those that feel the need to organise every facet of their life via twitter.
I like the Twitter support! A lot really.... it integrates all the IM in one place. Tweeting gets more familiar and easy.
You can send direct messages by chating with that contact the same way you'd do in MSN/AIM. There is always a group chat called Timeline updating the tweets being sent, where you can RT, reply and tag as favorite.
I think the IRC support was already part of libpurple, the Pidgin library that Adium is built around, but Adium's interface didn't support it to begin with.
It is OK for using direct messages as IM, but it won't replace your Twitter client.