I used AVG, switched to Avast for a while because of a conflict with ZA, but couldn't stand the look of Avast(sorry namtaf!)so returned to AVG. Yes, you can only set it to AUTO-update once a day, but you can often get extra manual updates the same day, and if you're on line a lot it's only 2 clicks away. I now use Sygate (still free)which I prefer to ZA; and from time to time I run A-squared, adaware, spybot and stinger. All of these are free.
I've never seen the appearance of the user interface as a significant factor in choosing anti virus, but when you consider the range of options available click here disliking the aesthetics seems an odd reason to return to something that's giving conflict problems.