And just one more question, how in the world do I know if my camera already has acu-mat or not?
A bit of an elderly thread here, but since much of the information is potentially useful to people interested in Hasselblads, I'll answer that last question.
Here is a brief guide to how to identify an acute matte screen:
(1) No matter what style the screen is, if it has the two semicircular cutouts on the edge of the frame near one corner, it is an Acute Matte D screen.
(2) If it is the standard focusing screen with the central cross, if the cross is gray rather than black, and can be felt to project above the surface of the screen, it is an acute matte screen; if it lacks the cutouts, it's a 1st generation (non-D) screen.
(3) No matter what style the screen is, if you shine a bright light through it (such as the light on your phone) and rather than getting a diffused, white glow coming through, you get a sort of starburst pattern with multiple rainbow-colored bits around the edges, it is an acute matte screen of either the first or second generation. Below is what you are looking for (the second image is intentionally out of focus overall, as that is the only way I could get the image of the effect I'm talking about in focus enough to be visible). Again, if it has the cutouts it's an Acute Matte D screen, and if it lacks them it's a first-generation acute matte screen.