I used x-chat for about 1 week, just to try it out. A great feature i liked in x-chat was the word replacement one.
Whenever you typed the word
hb, for example, the program would automatically replace it for Hurry Back.
This was a configurable feature, so you could adapt it for you pwn personal abreviations and setttings.
I think it would be nice to get sth like this on mIRC