I have just got Mixbus V3 installed. I am running the 64 bit version on Win 7. It is all running OK but still a little glitchy here and there. Crashes around changing audio buffer settings, opening and closing too.
PSP Xenon does not run inside Mixbus 3 at all well. There is something seriously wrong. Xenon is perfect for me inside other DAW's (SOP) But inside MB3 it only seems to be working on the left channel which is not much chop. Also it sounds like an out of phase sound with half the music missing and hollow, pretty weird. When you bypass it all is normal again.
I have quite a few of their plugins and they all work fine. Does not like Xenon right now for me anyway. I have alerted them to it in case they don't know. I bet an update will come out soon with some fixes hopefully this being one because I cannot use it all now as it is.
Other third party plugs work fine. I have the Nomal Pultec EQ and it is functioning normally inside Mixbus. I like Mixbus for mastering in some situations genre wise. I am about to master a more acoustic rock sound album so I think it will be perfect for it.