Finally snapped up this 4K trilogy using yet another free 30 day Prime trial, at around £22 for the three films.
Having only watched Shaun of the Dead 4K, I have to say that going off memory (I've seen the movie countless times on the 1080p blu ray release), that the image is surprising (because it's by Universal and is a cash in release) better by some margin mainly due to HDR/WCG, and decent level of natural grain and detail, in spite of it upscaled transfer.
However, I always thought that the original DTSHD Master Audio 5.1 audio was an absolute winner. For some years, I watched it more than once using the same setup with the DSU (Dolby Surround Upmixer, AKA faux-Atmos), and I'm not sure this was an upgrade. In fact, some moments seemed better to my ear with the 5.1 upmixed, over this native DTS: X track. Strange and disappointing.
Most people, including critical reviewers, seem to focus more on image and sound, I've noticed.
So, whilst the 4K image could be better for the format (it's still a step up over the 1080p transfer), it's a shame the DTS: X mix isn't as good as everyone seems to make out. Perhaps they never used either DSU or Neural: X for comparison before giving their rating?