This is my favorite paper, and also my tear-your-hair-out paper.
I've printed using 8.5x11 sheets, 13x19 inch sheets, 17 inch rolls and 24 inch rolls for about 3 years. I'm on a Canon iPF8100. I'm in hot and humid Singapore, and on a dry day the humidity is 70%, and most days are 80-100% humidity.
Printing with sheets has been the greatest nightmare. Even if the paper has stabilized to about 80% humidity, and is flat before feeding into the printer, when the printable side absorbs ink, the paper will become wavy, often parallel to the direction of the print head. And when the front end of the print begins to emerge out of the printer, the jerky paper feed motion of the printer pushing the paper forward actually causes the paper to 'flap' up and down, further increasing the risk of head strikes. My printer does not have the pizza wheels to tame the front end feed. My old iPF5000 had the drop down front feed pizza rollers, if the printer detects any flapping in the front. I would get a ruined print from those pizza wheels. Those days on the iPF5000 I would put on cotton gloves and basically use my fingers to guide the paper, and prevent it from flapping about, so the printer will not lower the pizza wheels. Unfortunately the waves still form from the paper buckling from the ink load, and I would have to set the print head height to "highest" to prevent head strikes. Now Harman Gloss is a rather thin paper for its weight (it is dense) and by setting the print head height so high, the spray from the inkjet head on the crest of the paper wave is smooth (because it is near to the spray source). However, the trough of the wave is very far away and the print area there becomes very grainy and mottled because it is very very far away from the ink head! It was deliciously frustrating because when I print images with smooth color areas like a lovely blue sky, I'll have a too obvious gradient of graininess consistent with the wave height of the paper. And still sometimes the print head will catch the edge of the sheet and leave ink stains. I can also hear 'piak! piak!' sounds as the print head collides with the paper edge when it buckles.
I resolved to use only roll paper then. Harman in rolls has direction and a sort of material memory, in that it bends in the direction of the roll and wants to bend that way. I've never noticed any waviness happening for the paper when printing from a roll, and I believe its because of the tension of the roll, plus the fact that the rest of the paper is still connected to a flat coil of paper until the printer cuts it at the end. And the paper path of the iPF8100 is such that the roll will press itself (due to its curl) onto the internal tray of the printer (the area where the print head moves back and forth as it prints), and it lies quite flat over the whole printing process. I can now set my head height to "lowest", and vacuum strength to highest. I know it sounds crazy low, but I have never had a single head strike since. No scratches parallel to the direction of the print head travel. And no uneven grainy prints.
There is another problem that I cannot solve. This paper's coating is just too fragile. I have to constantly dust the insides of the printer along the paper path to rid it of all the little particles. What happens is that as the paper is pulled along by the printer, little dust specks create streaks of hairline scratches, parallel to the paper path. If I forget to clean the printer first, I get like a thousand scratches. After cleaning I may get one or two, sometimes more if I'm not careful. And they will again appear at random, as the dust in the room settles again. I have never seen this issue with any other paper that I have printed on, and some days scarcely can believe how soft the coating is and how easily it scratches. They are very fine scratches, and ink does not cover them. Running an LED torch over the print reveals many inperfections. I am also getting a lot of holes and bumps in the coating of the latest batch of this paper. I've sent in samples to Harman/Hahnemuhle and they have been taking forever to get back to me.
Maybe others who have experience with this can chime in too.