Some of you get it - it's a simple matter of statistics and fact that, when you have conditions that are completely unrelated to the construction of the engine that contribute to failure, that engines that are in far greater concentration in the market will have the highest numbers of failure. It's probably safe to say that OS sells 10 or 20 engines to every engine sold by the next closest competitor. So, if all engines experience the same failure in the exact proportion to their sales, there will still be 10 to 20 times the number of reports of failure with the OS engines than any other brand even though it's completely unrelated to the actual construction or quality of the engine. Consider also the skill level of the people that own the various brands of engines and how they can influence the rate of failure. I would speculate that the average OS owner is less experienced than the owner of, say a Novarossi, Sirio, Picco, RB or other brand of engine. OS engines are the most visible and recommended engines, and newcomers may not even be aware that many of the other brands of engine are available. People that have been in the hobby longer are more likely to be exposed to these less-promoted brands, so they probably enjoy a customer base that is more experienced, and therefore less likely to cause damage to their engines.
Independent of the statistics, there MAY be some merit to one case being stronger than another, but some of the quotes posted here about what you've personally seen is ignorant of all the aforementioned. It's what's often called "science by a sample of one." Just because you see something happen once or even four or five times, it doesn't even begin to amount to evidence that there's a flaw. To actually find a legitimate flaw takes much more data and analysis, and none of us are in a position or are qualified to make that determination.
Merdith points to the OS carburetors as a problem, which ironically has been one of their most lauded accomplishments for decades. I've personally seen the extra steps taken in the manufacturing process to ensure their carbs adhere to very strict and repeatable tolerances, most of which are still not in use at any other engine manufacturer. The vast majority of experience engine people point to OS carbs as the standard by which all others are judged. But, perceptions being what they are, some people assume that, because they had a problem, it's universal and persistent.
Everyone is free to disagree because of their own personal experience, but facts and information collected over decades support the notion that OS is a top-quality brand that has the highest quality standards and has experienced fewer brand-wide problems than any other engine. I'm not suggesting they walk on water - of course they're capable of mistakes and have made some. but I've run through my share of engines (probably more than anyone on these forums) and these are my observations. I don't have any connection to OS, but I've been deeply immersed in the RC business since 1984 and have been running nitro engines even longer than that, so I think that lays the foundation for a much broader perspective. I give credit where credit is due, and they make an outstanding product. They may not be everything to everyone ALL the time, but on balance they're among the best, if not THE best in all matters of concern to the average nitro enthusiast.