I've heard they're best in full sun

Interesting @porkchop_z5b_MI as I thought I had read it 'preferred' less than full sun.

EDIT: Looking around more it does seem you are correct @porkchop_z5b_MI ie full sun is 'best'.

Whatever the conditions are where I've got it, it is very, very, very happy. Too happy. I've spent the last few years pulling out handfuls of it so it doesn't take over the entire bed. OTOH, when I've tried to transplant it to places where I'd like something to take over, it just dies. One of those places was very shady, so I'm willing to overlook that. The other was the steeper, unimproved east side of the slope it has been very happy on. So at this point, the plan is to let it expand in the direction of where I want it, then mow a path between the two parts, and pull it out of the garden bed entirely.

It is hard to tell how much sun anything gets in my garden because of all the trees. I call that spot 'full sun' because it probably gets a bit more than 6 hours. It does seem to appreciate good soil.

I planted it on a slope in crap soil in full sun. Like a lot of mints, it spreads and also self seeds. I think the central area often peters out but it survives through seeding and runners. Considering it is "Mountain" mint, I think the conditions I planted it in favored its thriving.

I was just at Coastal ME Botanic Garden last week and there were tons and tons of these planted along the sidewalks in the parking areas/main drive. Very sunny, hot and i imagine dry conditions. They looked outstandingly happy. They were quite large so I would imagine not newly planted.

I had them in a woodsy, part sun area that did not work. Transplanted to sunny rough edge of gardenbed and they are very happy; But they are sold in shade with other wild flowers at the nursery and they look ok....I think they are leggy there

They spread. I wouldn't buy a lot. Buy a couple see how they do and you'll sure know it if they are happy! Lovely smell, I like the frosted tops. And the insects sure like them. Certainly for the rough garden...