CLAMAV may not be your choice, but it works and isn't full of other malware as other so-called "free" AV apps are. I am helping folks all of the time who are infected by free security software that leads to nothing but headaches.
Not saying your link is bad, but I know that CLAMAV is clean, thus the recommendation. BTW, it works great on my system (W2K3). No bells and whistles, just gets the job done.
Actually, I think ClamAV is quite good. Note it's not a full-blown utility suite like NOD32 or Norton AV in the Windows environment. It's just a very configurable AV scanner. I'm going to guess the summation it 'sucks' is from a user who often uses the wrong tool for a job with the usual disappointing results. I'm also going to assume he/she tried it simply because it's a free product and they're too cheap to pay for something more suitable to their needs. No, it does not have a polished user interface targeted to those who prefer clicking on buttons to install and configure it, but it does have a lot of features (you actually have to take a couple of minutes to READ the documentation), a long history, and strong developer support.