The new Adium Version is now open for Beta testing. If you care a bout your system and only want stable software (haha!) don’t attempt to install it. But it is well worth the new features. A list can be viewed on the Beta page.
As noted: “Backing up a copy of the folder ~/Library/Application Support/Adium 2.0/ before using betas or alphas is probably a good idea.”

Most noticeable changes

Major AIM, ICQ and .Mac improvements. This includes working File Transfer, and faster sign on.
Improvements to the default look and feel of Adium.
iTunes integration is much faster, and updates as soon as the song changes.
Added global user profile and buddy icon settings. (Personal Preferences)
General Account improvements. Accounts can now be disabled when not in in use, and friends can now sign on from your Adium without saving their information.
Added an Xtras manager to better handle browsing and removing Xtras.
Major improvements in privacy settings.
Redesigned Previous Chat (Log) Viewer
Requires Mac OS X 10.3.9 or later (Universal Binary)

The longer, complete list can be found here.
Most noticeable on this list are:

• Consulted the Vorlon. <- which is awesome considering they might be blasting our planet to hell anytime soon
• Can now Get Info on contacts who aren’t on your contact list (#2424) & (#193) <- that one’s in there twice so it should really work now 😉
• Added more popcorn to the general preferences. <- might be good for the hours you spend in there
• Added a contextual menu for tabs (#1595)
• Added a contextual menu to make sandwiches tastier. <- nothing to add to this item, food is always good 🙂
• Message view window can now be transparent <- I’ve been waiting for that!
• Emoticon text equivalents are not expanded to emoticon images inside of URLs <- I’ve got to implement this into my AJAX chat too …no – to much work *g*
• Now with 200% more cowbell
• Added a dock-like autohiding ability for the contact list <- this might be worth trying out

That’s about it, read the whole list if you’re interested or don’t be a coward and just download it, install it, use it and report bugs to the Adium team.

Update:
Wow! Those folks are fast, we’re already on Beta 3 now.
Apparently they are so fast that they traveled into the future, releasing the Beta 3 today while it will come out tomorrow.