I always thought it would be nice if people in IMs could see what I'm typing, to feel more like a real conversation.
This reminds me a lot of ICQ's chat room. It was neat at first how I can see what everyone's typing in real time, but it's not so great when I become the one typing. However, most of the times I would prefer to be able to process my thoughts and perhaps check my grammar or spelling before I send it out. It's not always a good thing to be able to speak you mind and let the person on the other end to know about it simultaneously. From a reader's perspective, I would much rather read a complete thought, instead of having to wait for each word as they type. Showing that the person is currently typing is a good enough indicator that someone is trying to say something, so people won't be typing simultaneously.
2.4 statute miles of surgical tubing at Yale U. = 1 I.V.League