'Had the honor of meeting K37 last Sat. It was a pleasure I'd welcome anytime. I write 'cause except for the rare 'find', most of us only get to try the heavy sheffield 'silent' shavers, not the hard steels that have a better chance of providing feedback. Heavy grinds aren't for everyone, but how would anyone know unless they got to try some? Anyone w/ curiosity might do well to locate a nearby member that has or likes heavy grinds that wouldn't mind letting someone try theirs. A few strokes are worth alot of pages of opinions. At new prices, Harts are precious close to the price of the SRD special, which I prefer. The two Harts I honed & tested were wonderful shavers. While most call them silent, a very small amount of final strokes (for me, a total of 16" travel length)on .5 diamond brought its voice back. Like any near wedge, feedback is subdued, but doesn't have to be missing altogether. By comparison, the heavy Wackers, Swedish blades, some Henckels and Mr. William's blades babble their heads off.
On the razor burn - its not uncommon w/ the heavies, 'cause they tolerate more pressure than the full or extra hollow. The pressure is the source of the burn in most cases. They perform really well without pressure also.
Simple economics explains why hard steel heavies are so hard to come by. IIRC, there's only one place in the world that produces blanks now, apart from custom/semi-custom makers. If that's wrong - what is the right number? Two? They aren't making new blanks. That's what allows the market for custom makers that lack the costly equipment to execute a full or extra hollow reliably.
I'd encourage guys to give them a try - preferably before laying out all the coin for new. If you find you like them - don't be surprised if you like them *ALOT*. They have all the ingredients for an 'AD' of their own. If you don't like them - you've not torpedoed the shaving budget.
BTW, K37. The invitation is very much open for you to come try a smorgasboard of light and heavy blades.