I've used nothing but VET on my computer for the last four years and in all that time it has behaved flawlessly. Viruses have arrived by e-mail and been promptly announced and dealt with, including the one mentioned by DX Wombat earlier. Although I have heard of people having problems with other anti-virus programmes, I have never heard of anyone having difficulty with VET.
Automatic updates arrive almost every day and VET checks itself to make sure all of these have been received. Once a week or so I scan the whole hard drive to make doubly sure but otherwise VET does everything itself ... and for a techno - retard like me that's great. Recommend VET very highly.