Because of its free version, many believe its weak. Believe me, its one of the most secure and stable AV in the list today. I agree with reputed ones, but u must consider results and detection ratio and its performance are far better than them.
Avast on Hardened Mode set to Aggressive provides excellent protection and hardly "weak".
Kaspersky,ESET,etc. require some tweaking to squeeze the max protection out of them.
I have put Avast Free on a lot of PC's for average users and those who kept it updated remained infection free however nothing is 100%.
Kaspersky & Norton are very good programs but so is Avast.IMO Avast gets a bad rap for having a free version and everything free is not necessarily good however Avast is.
After some time testing my system speed I am back to Windows 7 Professional. Several reasons :
Incompatibility of my integrated graphics with Windows 10. Needed to use some third party fix for being able to bypass WDDM
Real feel that my system is more responsive
No Avast freezing problems and improper disablement of the Windows Defender in Windows 10
Proper driver installation of my AHCI bus which made +70MB boost in read/write performance of my SSD
Personal feeling of having more control over the OS
If I had newer laptop it would work fine with Windows 10, probably, but since Intel decided to leave us without the proper drivers for Intel GMA 4500 MHD and a 1/3 of the chipset, I had to make this move. I probably won't come back to Windows 10 until I buy a new laptop.