Via the Unofficial Yahoo Blog

Yahoo Messenger has been picked as Editors Choice by C|NET in a review of the top four instant messenger programs (AOL, ICQ and MSN being the others)

Yahoo pipped the others by having the most customizable interface, and lots of features built in:

Yahoo Messenger 6.0 is known as the Swiss Army Knife of free IM clients for Windows. To name a few, Yahoo Messenger serves up a radio, games, a stock tracker, weather, and a calendar/day planner along with regular IM, chat, e-mail, and user-management functions. If you want a lot of bells and whistles to go along with your IM and chat app, choose Yahoo Messenger.

The main area it lost points for was the lack of support avenues (only an online F.A.Q. is available.)

Personally, I like Yahoo Messenger and use it everyday, but there are some features that I would like to see improved:
· Optional radio and games - like the review says, Yahoo is pretty hefty for an IM program at 11Mb when installed, it would suit users who are just looking for IM better if these were optional.
· A search facility on the message archive - maybe I'm the only one, but I'm constantly looking back through my archives for URL's, Yahoo should make this searchable.
· Save the messages archive on Yahoo's servers, rather than the users computer, so it's accessible from any computer (like most aspects of Yahoo accounts are)
· A description of the emails that are in the YMail inbox in the overview - at the moment this only tells you how many mails you have with no other information.
· Have as opt-in installing the Yahoo toolbar, making Yahoo the default search engine and changing the homepage - rather than the current way where all these options are checked when installing YIM.

Info:
· Yahoo! Messenger
· IM invasion: top chat apps compared
· C|NET Review - Yahoo Messenger 6.0