A lot of folks over at the Concours Owners Group purchased and evaluated the Ibuki. Here's a link to the thread:
https://forum.cog-online.org/index.php?topic=62162.0
My own experience thus far is very positive, but I want to point out a sizing issue that I experienced. First thing to note is that the Ibuki uses two shell sizes.. one for XS, S, M and the other for L,XL, XXL.
My measured head size is 58cm, and this is at the top end of a medium (57-58cm) per the Kabuto sizing chart cited on the Revzilla page, So, that's what I bought. I wanted a snug fit and the smallest shell size, but the Medium was just too tight even after wearing it many hours over the course of several days around the house. In addition the ear-pockets didn't line up with my ears!
I temporarily kept the Medium but bought a Large to compare against the Medium. The Large fit me better..not overly tight and the ear-pockets lined up perfectly with my ears (due, I suspect, to the larger shell size). Interesting that the Kabuto sizing chart stated Large as 59 - 60cm yet a tag on the helmet itself stated Large,58-59cm. So I really was right on the cusp of Medium and Large. If you're right between Medium and Large, you might want to try both as I did. I was able to return the size Medium to Revzilla by paying the $7.45 return shipping.
To get the Large to fit just a tad snugger , I purchased size Small cheekpads also from Revzilla. There are 6 different cheek pad sizes available to customize the fit and they are interchangeable between all the helmet sizes.
Oh, by the way, as Revzilla honors price matching, I paid $249 for the Ibuki.