Museum Etching is absolutely my favorite fine art matte paper. It is also the most expensive paper that Hahnemuhle makes for inkjet printing. It costs quite a bit more than Cold Press Natural. The last time I checked, it is the most expensive branded inkjet paper, apart from specialist varieties.
Museum Etching is very luxurious and very thick. There is a warmth to the paper, and it feels soft, in a comforting way. It is not typical of a real etching paper, in a good way. It is truly beautiful to present in a folio box. It's surface texture is unlike any other paper I have experienced so far. It is very organic. This paper will not boast the widest gamut or the greatest dmax of the matte papers, but the way it carries ink is just beautiful. It can take a lot of ink without any uneven sheen or mottling in the darkest tones, which a great number of matte papers suffer from if you look at it hard enough, in relatively strong directional gallery lighting. However, Hahnemuhle's QC has been very bad of late, and I find myself throwing away about half of the prints I make because of surface imperfections, cotton seeds embedded in the paper and rarely, flaking of the coating. But when everything comes together, its really a thing of beauty.
I strongly dislike matte papers with a surface texture that appears manufactured. Epson's Cold Press papers have a surface that appears stiff and ugly to me. It does seem to be able to take high ink loads too, but I never liked it enough to print much on it. It says here
that the base weight is 340gsm, but our local review
says its 330gsm. B&H lists the 24 inch roll at 500gsm which I doubt is true. Epson lists the sheet version at 21 mil thickness, but the roll at 19 mil. Museum is about 23.6 mil. The weight for the roll version probably is lower - just be aware when you're buying paper. Other's who purchase sheets and rolls please help confirm if this is true. Many reviewers agree that this paper has a huge gamut and deep dmax. If these are qualities that suit your images, that this paper is worth considering.
I tested Canson's BFK Rives, their most premium offering, and found that their paper flattens very well after printing, better than Museum Etching. Many matte papers perform similarly enough that I tend to pick my favorites based on its surface. Unfortunately BFK has relatively deep 'pits' in its surface with annoys me, and doesn't replace Museum Etching for me.