I use the enterprise version of eTrust. There is far fewer cases of false positives and, in my view, faster response times to new virii. The catch: You pay more for it, but that is generally how the system works for everything.
I still think that a virus/trojan detector built into mIRC is pushing sh*t uphill (an Aussie way of saying 'waste of time'). This is because:
1. Someone has to keep the updates coming along. Does Khaled have the time or the resources? Probably not.
2. Many trojans that affect mIRC are mere mIRC scripts which are either CTCP backdoors or socket bots and hence are legitimate code even if the purpose is less than desirable. This means that either some trojans will never get found or you will have mIRC deleting bona-fide mIRC scripts all the time.
In short, I say leave it to the AV companies.