Pros: Possibly still has a good detection rate (about 5 years ago it was the top pick of free AVs)
Cons: Used to be a light AV and very good for older or low-spec computers, but has grown into a huge and very cpu-demanding AV. Slows the system down remarkably.
A very annoying nag screen with ad for their paid products pops up on every update. This is not freeware, it's adware.
Other Thoughts: I have used Avira for years but, uninstalled it earlier this year. It wasn't until it was gone that I realized how much it slowed my computer down. I now have Avast running on my XP, windows 7 netbook and my windows 8 laptop.