I absolutely love MSN 7.x It's probably the best IM service in existence, with the least intrusive interface and the best options. The only problems are the ad at the bottom, and the fact that you can't have it log events (like when people log in, log out, or message you, or when they go away, go busy, go brb etc...). Trillian does that but I just don't like using Trillian when I'm only using the MSN service and only need a few simple things.
I also noticed that, along with Windows Media Player, MSN 7 is also compatible with iTunes to display the songs you are listening to. Just thought it was cool of MS to allow the two to be compatible.