you guys have to admit that its also a big hassle. No subject header. Also quite slow. And AT servers aren't the most reliable. The big pain i've found for selling and trading is that people will often forget to reference the previous message...and without subject, or copy...you have to dig through the history.
The fact that you have to actually refresh the website makes it very different from AIM. Its not instantaneous.
I think its just the geeks in all of us especially those at AT who enjoy running their own server...not that there's anything wrong with that , afterall, I run my own exchange server for 2 people.