Thanks guys for the congrats - I hope it didn't come across like I was swooping in to fish for congratulations. I just saw an opportunity to contribute something relevant to a thread that I enjoy following, so I did.
Smoove - this race is definitely worth trying, and perhaps the rolling aspect might help your cramping. I do think that this is not the best course for someone who is a rhythm runner (as I am). The rolling nature, with virtually no flats, makes it very hard to lock into a pace. The runner who will do best on this course is someone who can handle variations in pace and surging, since the course effectively makes you do that.
I think if nothing else, you would enjoy the experience. It really is a unique race - the photo-negative of Boston.
Like Boston, you run from a suburb into a city, and the course is a net downhill. But where Boston is about celebrating running, and many people just run it "for the experience," CIM is all about chasing times. There were very few people on that start line who were running the race just for the experience; the vast majority were deadly serious about hitting a time that mattered to them.
[as an aside, I didn't see a single runner in costume or juggling or anything like that the entire race - again, very different from most other marathons.]
As noted before, the logistics for CIM both before and after are vastly superior to Boston - this is a race managed by serious runners for serious runners - money is spent on stuff like extra portapotties and heated buses, not bands on course and photo opportunities.
I found the first half of CIM to be tougher than the first half of Boston - much more climbing. And while CIM does not have Heartbreak Hill or anything like that, the hills aren't truly done until Mile 22. And those last four flat miles feel awful by then, if you've wrecked your legs on the previous course (as I did).
I do think that the more one runs this course, the better one can run it - you just don't understand (and thus respect) the course until you've run it. A lot of people blow up here each year, and my sense is that most are first-timers who see the profile and get cocky.
I know of 12 people who ran CIM whose training I am familiar with. Three set 5 minute+ PRs, though those PRs were consistent with what previous races had indicated - nothing shocking (and one of those was a 7 minute PR over CIM 2017...). The balance missed their realistic goals - some by a little, one by a lot (that person went out WAY TOO FAST and paid spectacularly in the final 10K, finishing with an 11 minute positive split). For the rest who missed their goals, it was a combination of having an off day and not respecting the hills quite too much (several still ran well - just not quite what they wanted).
So that's 25% of those 12 who had really good days, and 75% who didn't. I think that when discussing the spectacular results of CIM, people focus on all the good races that happened (and there are a lot of good performances, when you have a field of this caliber), and don't pay attention to the balance of the results.
I also think that, regardless of how well you run this race, it will wreck you - it's the nature of the course. I am much much more sore than I've been after any other race in the past several years, including Boston 2018. I feel this course is harder on the body than Boston (though my body might have just been preserved by cryotherapy at Boston). I'm hearing similar from everyone else who ran it this year.
StillImproving and Cocoon - congratulations on your great days. RunnersFix - I'm sorry about your day. I absolutely agree with you - the course can be very fast, but it's not for everyone. I know others who missed OTQs for similar reasons to you. And like you, they are looking for flat races for their next attempts.