I bought a bottle and, to me, it's nearly identical in color to Diamine's Prussian Blue. Manhattan Blue may be just a touch grayer, but it's very very close, imo.
Right now, it's in my new blue Pelikan 605 (M) (the one on sale at Fahrney's) and doing splendidly.

Edited for mistake when trying to answer when I'm too tired...

It's the Prussian Blue that's a bit grayer, not the Manhattan Blue. At least in daylight and under my full-spectrum light (Ott) on Clairefontaine. On off-white paper they are closer in color, I guess because the MB does gray down on such a paper.
And added: When I bought MB and C d'A's Storm from Art Brown, I did wince at the shipping, but to be fair, they sent it FedEx fast and it was packed well.