I have lost faith in the WMF and EMF file formats for one simple reason: neither of these formats can accurately retain the fine curve data of a true vector file created within PPT.
Proof: Typeset the word "Test" in Times Roman in Illustrator at around 100 pt. Convert type to outlines. Export your beloved WMF or EMF file. Place the file (insert picture) in PPT. Zoom into the image so you can see the serifs (you may have to enlarge the imported object. Tell me the curves of the imported file look great... I dare ya.
This type of curve distortion is unacceptable and dangerous, especially if you are importing a WMF / EMF file of your company's logo. You can minimizethe curve distortion by enlarging your source image to approx. 400% largerthan you plan on using it within PPT, but it's still there.
This issue of cross-software compatibility is a major problem for anyone working as a professional visual communicator/designer. And it's so importantto the software programmers that they have not resolved it in over 2 decades of software versioning and upgrading.
Classic case of not listening to your customers.