I've used Eduard Zim on a Tamiya Panther G. It's in mid-construction and not painted, so it's a little hard to judge exactly how good it is, but I think it'll look pretty convincing when finished. As Tigerman says, it is quite uniform, so it clearly represents a neater than average Zim application, but there are photos that show German tanks with neatly applied Zim, so I don't think it is unrealistic. It does lack some depth, an it might be a little underscale in that regard, although most putty applications end up being overscale, so pick your poison.
I glued the stuff down with superglue, applied around the edges. I also had drilled holes in the tank which I used to glue the Zim sheets from the back, so that there would be tacks in the center as well as around the perimeter. I think that maybe the trickiest part is blending the edges which I have done with putty. The one shortcoming that I have seen with many PE Zim applications is where the edges are obvious making it look like sheets of zim glued to the tank.