I have currently equipped it with the Kaweco Premium EF Nib and it writes and feels wonderfully in the hand.
I have come to like to Demonstrator pens as they are rather neutral and don't imply any colour. I always want to make sure that ink and pen match and the neutral colour makes the pen flexible.
That being said, it's inked up with black, but in general I have a hard time inking for example my "Deep Sea Blue" Platinum pen with anything else but blue-black.
But that might be just me.