I used AVG for a few years now. I have never trusted anything all in one. I would go with Avast now. Avira has better detection and better heuristics. Avast has a much better update system and each update is small and quick.
I use Opera and firefox both. I have not yet update the latest Firefox 3.7 Alpha 4. Opera always is customizable enough to make it possible to move tabs above or below the address bar. Who knows Firefox will eventually be usable after all.
I use avg as its free and a good anti virus software. It works well for me. I have never had any problems with viruses or malware. Kaspersky is the best one. But not free.