Not only I have tried but experienced it many times and enjoyed it ... with the right partners.  Only a few times it was  "... meh ...".
For me, the best part of a MFM is to see the girl having fun and loving it.  That is what turns me on.
I even like to do do a double barrel BJ.  I think many girls like it.
My goal on MFM is to have fun with the girl.. not to checkout other john's jr.
I have no problem being naked in front of other guys because 
I don't care.  I see this as the same as taking a shower 
- at the gym
- after a hockey match
- at the military cadet
Men should be comfortable with their body.. big, small, thin, large, etc ...
I hope this will enlightened guys who think MFM is a gay tendency.  But yes, friendly fire can happen.. Just aim properly 
 
Just sharing my thought and not judging anyone.