Comodo Anti Virus is an interesting project, unusual among freebies in that the project is funded by other Comodo divisions, not by sale of a Pro version. As a result it's not feature reduced, there appear to be no licence limitations for home or commercial users and can be installed on a network server.
I'm test running it on a backup machine and so far it's been fine.
On the down side, as you say it's a beta and there are a few niggles with the way some parts of it work, but the development team are on the ball and open to suggestions. The shield function is "On Access" which means that it will not stop you downloading infected files, but will step in when you try to run them. Not on a par with the best available.
It also remains untested by ICSA or VirusBulletin, so educated independent comment on how effective it is has yet to be provided.