I could, but I regret the day I turned that on on my 360.
The teenagers would love it, and yes, it would be nice to have if there was an easy way to turn it off/ignore incoming/flag as off-line. The problem with the 360 implementation is that once you turn on the console I get annoying messaging pop-ups and it's not easy to turn off.
But a way to integrate aMSN would be nice.
I agree IM would be a great feature overall... and here in Europe its possibly the killer app for many people. At present until we have that capability built in I use http://www.meebo.com
from either KDE or just from "Computing" and open a browser window and then go to Meebo. Its all browser based and works great for MSN/AOL/Gmail etc