I love it when people blast pieces of instant messaging software, especially when they cite a lack of features. I don't know about you, but iChat has a decided lack of features when compared to a lot of other clients.
Either way, Microsoft Messenger gets a lot of the same kind of flak that AOL Instant Messenger gets. I presume a lot of it has to do with the fact that the word "Microsoft" is in the name, which apparently connotes that the product is entirely un-Mac and, therefore, eeevil.
The fact of the matter is that Microsoft Messenger is as capable as just about any other messenger out there.
A lot of people don't remember how broken MSN Messenger was just a few years ago. There was no video, no audio, barely any features at all, which opened the door for some competition from sources like aMSN, Mercury Messenger and Mac Messenger.
Since then, though, Microsoft has turned this little train around and made something that is actually usable. The fact that Microsoft seems to be committed to developing it further, such as in the recent addition of video and Yahoo Messenger interoperability, tends to make me look favorably on it -- even if it IS made by Microsoft.
Do I use it much? No, but that has nothing to do with my dislike of it, but simply due to the fact that I know very few people that actually use the network for communications.