Martin
I just got off RCGroups - engines thread after doing a search on MDS engines. I cannot say I was surprised with what I found, and one guy summed it up very well. I am quoting:

"When I started flying a gentleman at our club flew nothing but MDS and had the same or better reliability than any other group of engines being used.

IMHO there are two kinds of engine people.

1. Don't bother me with the details I wanna fly.

2. I want to understand when my engine is "talking" to me and enjoy the mechanical bent to the whole process.

This is not meant as criticism IMHO one group is not better than the other they just have different needs.

If you are in group one stick to the major name brands built for the "everyday" flier.

If you are in the second group you shouldn't shy away from an MDS."

I belong to group #2 and may be prejudiced, but - believe that most nay sayers have not tuned too many engines properly in their modelling career. That realization came pretty loud and clear going through the postings. It reminded me a guy who was lamenting his ST 4500 was going through 32 ozs. tank in 8 minutes. At the end he admitted that he runs 30% nitro and 20/20 fuel in a TF P-51 clocked at 125 mph. To me - that clearly demonstrates utter ignorance!
I will bench test my MDS 2.18 and report the results.
Joshua