I haven't tried any Iroshizuku inks, although I'd love to. The price keeps putting me off. I wouldn't have sprung for the Edelstein, except it came free with my M600. I certainly don't think it's worth four times the price of a bottle of Diamine! That said, I'm really taken with the J. Herbin and that's a bit pricier so I could be tempted...
In reference to your second post, I've not tried any standard Pelikan inks, although the Brilliant Brown is piquing my interest. Would you call them wet or dry?
Thanks for all the details on the inks and pens. I keep dithering over a Parson's Italix; they sound like nice pens, but I am not grabbed by the look. I will probably pick one up anyway.
The Iroshizuku inks are lovely and well behaved. They are unusual, pretty colors, and I enjoy them. I admire more colors frequently, but have only two full bottles right now, Asa-Gao, and Momiji. Asa-Gao is a beautiful blue, but also usable as a daily writer. In a P51, people think you're using a ballpoint. Momiji is a slightly orangey salmony red. Clearly red not pink, but not a fire-engine solid red. It is quite bright, and would mark up other things quite notably. Many people prefer Kon-Peki to the Asa-Gao as their go-to blue. Kon-Peki is almost a turquoise - very pretty, but too light for my daily writing. Neither are water-resistant in the slightest.
They're expensive, though, and I can't say they're so good you must, must, must go get some. Samples will be your friend to see if you love it.
Everyone tells me the Pelkian 4001 inks are dry, and I guess the Brilliant Black is a little dry. It's the first ink I put in my Lamy 2000 and the two just sing together. I've tried others, and they're not as great. They work - I haven't had any trouble with the 2k not writing - but the Brilliant Black is just perfect. I have many other inks to try in it, though, so probably will, eventually.
I wanted an ink from a pen manufacturer, so got the Pelikan. The Namiki Blue (also a nice ink) and Iroshizuku came later.
I bought a bunch of the 30ml bottles from Diamine as a way to get a wide selection of their colors. I'm in the US, so no VAT, and the flat-rate shipping means "buy many bottles at once". The little bottles are not expensive, but a much bigger dose than a sampler. Lots of fun and a great way to try new inks. I'll have to try some Oxblood next time I get a hankering and order some. They're about $5 USD each, plus a little shipping. The Goulets want $1.25 for a 2ml sample... If there's a chance I'll like it, the bottle is a better deal. I bought mostly browns, and the ingredients to make a faux parker penman, which I still haven't tried.