I use MSN Messenger all the time, only because most of my friends use it. MSN Messenger isn't very kind for Mac users, because they tend to be very bugging and logs you out every now and then without warning. Sometimes it logs you out without you even knowing that you were logged out. Still, I stick to it because I haven't got much of a choice, since my friends are all using it.
I do, however, use Skype quite a bit. I didn't like Adium when I used it for myself, but I imagine that is purely a personal taste thing. It is highly recommended in other websites, so you could try that one out yourself.
But if you are like me and you really need to use MSN Messenger, then use meebo.com as a client. It is browser based, and it allows basic chatting functions. But check the version of your messenger anyway, make sure that it is version 7.0.1.