I haven't logged this story before today, but over the years I've read it many times. It's in a horror anthology that I've had for decades, and it's always been one of the highlights of that book for me... a Lovecraft story that I enjoy unreservedly. The focus is solid, the prose is - for Lovecraft - restrained, and it's uncluttered in nearly every respect. It's no secret that I find Lovecraft's storytelling to be both overwrought and overburdened, but in this he's got the balance right. The effect, for me, is horror and not hysteria. I have vanishingly little patience for his particular brand of hysteria, but the narrator of "Pickman's Model" is so solidly reliable in his telling that the disturbing nature of what he relates is effectively emphasised. 

It's the best thing of his I've read, and by some margin.