I have not encountered any problems with Weapon for FSX in Windows 8. It works perfectly for me.

As with Windows 7, I had to run the Loader using "Run as administrator" to add it to other aircraft.

I'm not talking about installing the software using the Run as administrator. I'm talking about running the Weapon for FSX "Loader" using the "Run as administrator". I don't always have to use it either, but sometimes the Loader fails to make the changes required to add the weapons to an aircraft, using "Run as administrator" prevents that from ever happening. I'd rather just do that, than add to an aircraft, start FSX and then find that it isn't working on the aircraft I just added it to.

Out of curiosity, what setting is your UAC set to? Mine is set to the default setting, which is 2nd from the top.

I rarely use the ACE for the Captain Sim aircraft. I set all the aircraft up once when I first install them, then I make the rest of the changes in the Aircraft > Fuel and Payload menu.

Sometimes it depends on which version of the OS that people are using. Like Windows 7 Home Premium is more strict than my Windows 7 Professional. I don't know why it is that way, but I'm always get caught out by the difference on my wife and 2 sons computers because thy all have Windows 7 Home Premium, with the UAC set at the default setting.