I know a lot of the war gaming and military modelling fraternity scribe and emboss finishes into a foam-like material. It seems to get results very quickly and, done well, can look very very convincing.
My main concern with that approach is that if something is very easily scribed then it's also very easily damaged. Not a problem if put on a layout and never touched or gone near again but... Having at first hand seen what layouts have to go through when exhibited, I would always worry that the exquisite finish could be trashed in seconds.
I have used DAS before too, quite a lot on my 4mm clay branch layout Polsarrett. I quite like it, particularly the stone effect variety they make. I don't think it's any quicker or easier than my other plasticard based methods though.
What I always try and aim for is a finish that doesn't look like sheets straight out of a pack and stuck to a model. My pet hate is to see buildings and structures with no attempt to hide sheet or corner joints. (That's a particularly a problem with the same Wills sheets IMO). As soon as you see the sheet, you've destroyed the realism.
On the other hand, I really like and appreciate work such as that done by Geoff a few posts earlier.