I can't say for sure but it is often talked about in the forums that ITW (in the wild), first then, it would depend on the seriousness of the infection. Worms and Viruses would I assume receive a higher priority than sat Adware, etc. But I don't concern myself with the priorities just ensure that mine are up to date.
Keyloggers are covered it often picks up user installed keyloggers that monitor activity on their computer. However, avast isn't a specialist anti-spyware/adware and you should also have an anti-spyware application installed.