Appreciate the review, and the honesty of it. I tend to like blue-blacks, but I agree with you that this ink lacks blackness. On my screen, I just see a dark blue ink, not something I would call a blue-black. Personally I find it informative to read about inks the reviewer doesn’t really like ... an unbiased personal opinion is always valuable. The fact that it stains your pen is certainly viable info ... I’ve never bothered giving this any attention before ... I typically clean my pens after each use (and never fill them completely because I like to cycle between inks), so I’ve never had any trouble with staining (well... almost never... Pelikan Edelstein Star Ruby took a while to clean out of my pen, but that’s the only one I can remember).
I think in some ways, negative reviews are more useful - they can tell you what to avoid. But I have to say, my Metropolitan loved this ink, and it is quite pleasant to write with - the extended "cap off and idle" time is convenient too. So it's one of those "know what you're getting" situations. I would still recommend it to anyone who needed a large amount of inexpensive ink - say for work or college notes - this would be perfect for that.
Sailor Nioi-Sumire, the ink I just finished with, also needed pen flush, but just to get rid of a line in the clear section where the converter stops, basically. If the section weren't clear, you'd never know it had left a line. It cleaned up everywhere else easily enough, but that line took a bit of soaking and shaking in a sample vial filled with pen flush. I've discovered that the Penmanship section (sans nib and feed) will fit perfectly into a sample vial filled about half way with pen flush. Makes it easy to clean.