Not a problem
On my systems I run avast, IOBit ASC6, Malware Fighter, and Zone Alarm. Same versions I ran on XP. No problems.
On the issue of Security, Win 8 doesn't seem to be any better or worse than Win 7 or even XP. Since it is a fairly new release, the hacker community hasn't had time to design an effective attack so it will be some time before we can echo MS's claim. Hey, they wrote the OS but couldn't build an effective maintenance package that works effectively so how can we accept their claims?