I've recently purchased avast AV pro, and I'm pretty happy with the product.
I'm a little disappointed, however, with the online security add-on to the browser, I think that it actually contribute to the spam,browsing inteference and online tracking that it supposed to block.
By default, features like communityIQ (sends data to avast servers), Safeprice (which tracks my sites and offers me deals...really?), and Search engine results which highlights search results pages are enabled. Those are essentially the tracking tools that the add-on is supposed to block. It's ok to have them, but they should be disabled by default.
Another example: I received a message from the add-on that the Adobe PDF extension on IE is rated poorly and it is recommended to remove it. Fair enough, so I've asked to remove it. I was surprised to see a message that I have to choose Yahoo or bing as a homepage in order to remove the extension. Why is that exactly? I went to IE settings and removed the add-on myself...my home page remained the same.
I understand the need for these features on a free product, not on a paid one. For now, I removed the add-on...I'm still happy with the AV, though.