Well, my laptops both came with Norton, which my IT guy said it's a total piece of c.rap, and recommended me installing Avast instead, which is very good and also free.
Since I was curious, though, I also tried Avira, AVG, and Eset for a while. Honestly, they only gave me a headache, each time I used them. AVG was the least annoying of the three, but it consumes a lot of RAM. Avira was always giving false positives because of cracked programs (AVG did that too, but not all the time). And Eset is paid, and I found the trial version quite overwhelming, because it was always scanning and scanning and scanning.
So, from personal experience, I'd recommend using Avast Free, but it also has a paid version, if you'd like to try.