If you are running 32 bit, do NOT buy ANY PMDG product. Eventually either the PMDG Options dll or the dll.xml file will become corrupted and any PMDG product dependent upon it will stop working, such as from the 747-400 on forward. PMDG has no interest evidently in supporting their own product. This is the reply I got from product support...
"I just noticed in your reply that you are running Windows 8, which is not a supported Operating System for any of the current PMDG product line. The DLL issue is becoming fairly common for Windows 8 users that has been extremely difficult to identify but we believe that it is an issue with the way Windows 8 tries to protect the operating system. There aren't any good work arounds for Windows 8 currently, so our current recommendation for FSX users is to turn Windows 7 X64 for proper operation."
So PMDG is saying that their software is obsolete and will only work with obsolescent operating systems that Microsoft will likely cease support for within a year. And further, they appear to have no interest in fixing it.