I recently took part in a TopCoder Single Round Match (SRM), which ended up being very difficult. You can see the overall statistics here — out of 557 people that opened the easiest problem (ie took a look at the problem description), only 223 (40.0%) got it correct. In my (limited) experience, that’s a very low number for the first problem on an SRM. It was also a 300-point problem; usually the easiest problem is worth 250 points, which means that this problem was significantly harder enough to warrant a score readjustment. This is compared to the last SRM where 487 out of 656 people solved the first problem (74.2%).
Not only was the first problem much harder than usual, the second problem was extremely hard. To be precise, extremely few people solved it (or the third problem), which could be due both to it being difficult, and people running out of time by spending it all on the first problem. But still, the stats speak for themselves: only 23 people solved the second problem, and 9 people solved the third problem, so only 5.75% of people who attempted the first problem were able to solve one of the other two problems (well, less, since there were some people that got all three). Comparing it again to SRM 454, in that SRM 314 people solved the second problem, so almost half of the people that attempted to solve the first problem solved the second. That fraction is 10 times higher than in the SRM I took part in. Suffice to say, the scores were very low.
In fact, getting a 0 in this SRM actually had a good effect for some people. Take a look at the rankings for my room. Three people who got zero received between 15 and 18 points, so it seems that if your ranking is low enough, you can just enter difficult enough SRMs to improve it. Though the guy who had a ranking of 1939 but got a zero lost 160 points, so it really only works if your ranking is low enough. But whatever you do, don’t get a negative score: the people that did that all saw their rankings go down by >100 points. It seems that missing that one challenge will put you below everyone that gets a zero, so your ranking ends up being very bad (ie near the bottom) and you lose big. I, for one, am not very good at making successful challenges, so I will keep this in mind when deciding whether or not to go for that risky challenge.