Usually it starts out well, and then begins to slow to a crawl. If you are using your carriers direct connection, your carrier will prob. slow down your connection until you lag off. They don't want you using too much of their free bandwidth. Logging on to IRC chat with your cell phone probably won't be real successful if you want to stay online a long period of time. If you can find a good, strong wireless connection, you will prob. have better luck.
As an aside, when we used AT&T I could not connect to any efnet server. They seemed to have CHAT blocked altogether. Sprint does allow me to connect, but that connection will slow down quickly.
Hard to say, I get logged out quite a bit as well. It could be a problem with our session system. I'd like to upgrade it.