After 7 to 10 days of heavy studying, I took the test and passed it with 90%.
On one side, I got lucky for not getting too many tricky or very hard questions.
That said, it took that long because I just didn't cram for the test, I read the PIC instrument book twice, all the relevant FARs, Aviation weather, portions of AIM (I have to read the rest now), studied charts, and took an 8 week IFR ground school in 12 hours :)

The only question I got and that sucked was the one where you have to build an entire flight plan leg by leg, computing time, cross wind, fuel burn, and in both directions, just to answer a single question of how many minutes you can stay in the air before you have to turn around for fuel. The question wouldn't be that bad if the answers weren't spaced out by just 3 to 5mn, making it very easy to pick the wrong answer if you try to do a reasonable approximation instead of the whole 30 to 60mn of computing.
That's just silly in my opinion, and I told the FAA so much in my feedback. In the end, I just didn't feel like doing all this silly paper math in the day and age of electronic flight plans and computers (I've done it on paper more than once for my private, that was enough), and I just put answer at random.

The other problem is that it's frustrating that they don't tell you which specific questions you made errors on. They only give error codes which could refer to one to 20 or more questions.
I looked mine up in the Gleim book, and for at least 3 of them (one is a 1-1 mapping: H945), and I can't see how I made a mistake on them, especially on H945 aka 11-10 which had an answer of 139KCAS or (B). I know I computed and answered that, and my E6-B computer still has the correct answer dialed in. Yet, I still got the answer wrong according to their report :(
It might be that somehow I clicked on the wrong button, and really made a mistake on the 2 other questions I think I most likely got right too, but none of this would be happening if they were more transparent and gave you the exact questions you got wrong along with what answer you gave.
At least, it's not as bad as my private, where I could swear I knew almost every single question and answer, and somehow managed a 88% (in this case, I felt a bit more shaky on some stuff, despite much studying, and did better comparatively)

Anyway, despite all those little details, even if vexing, 90% is a passing grade. I'll be taking the rest of the day off, and go back to the books to finish up what I haven't read entirely (aviation weather services explained, and all of AIM)