I have been running APV in both of our M sleds for a few years now, and each year the valves look pretty clean. I mean the oil works, it does not smell great, and it is definitely not cheap, but it has worked for us. I usually buy it by the case, and get a pretty decent discount, so its not so bad. My dealer sells Yamaha as well, he rents mostly all Arctic Cat sleds, and each cat gets the Yamalube 2S mineral based oil. This is the cheaper stuff, but if you keep the valves clean it works as well. He has put tens of thousands of miles on these rental sleds year after year, all running Yamalube 2S. He has not converted me over yet, but the proof is there that it works. I do think it has an unpleasant smell though
Now I know many guys who run Redline, and to me that is one of the best 2 stroke synthetic oils on the market. Very clean burning, little residue on your valves, and smells decent. It is pricey, but to some extent you get what you pay for with oils.
John