They work well together as my signature shows.
For avast! IS you will have to exclude MBAM services though.
How will i do that?
add these exclusions in file system shield/ exclusions and settings/exclusions, you'll probably have to copy and paste each one seperately, they might not be needed but they are here if you want to add them.
C:\Program Files (x86)\Malwarebytes' Anti-Malware\mbam.exe
C:\Program Files (x86)\Malwarebytes' Anti-Malware\mbamgui.exe
C:\Program Files (x86)\Malwarebytes' Anti-Malware\mbamservice.exe
C:\Program Files (x86)\Malwarebytes' Anti-Malware\mbam.dll
C:\Program Files (x86)\Malwarebytes' Anti-Malware\mbamext.dll
C:\ProgramData\Malwarebytes\Malwarebytes' Anti-Malware\rules.ref
C:\Windows\System32\drivers\mbam.sys
C:\Windows\SysWoW64\drivers\mbamswissarmy.sys
C:\Program Files (x86)\Malwarebytes' Anti-Malware\*
C:\ProgramData\Malwarebytes\*