Just beaten this, thoughts below:
+Vastly improved performance over New Blood, runs at a steady 60fps most of the time with a couple of slow downs during combat in the old town to around 45fps. Given I'm using higher settings than New Order I'd say it performs at least 100% better.
+More of the same which is a good thing - much better than the older Wolf games like RTCW and Wolfenstein
+Zombies are good as not too creepy, retains the fun vibe from NO
+Nice easter eggs
-Ends a bit abruptly, I was expecting something after the boss fight (which felt a bit 'random' to be honest, like they'd just chucked a bizarre monster in because they couldn't think of anything else to do). The percentage on the loading screen is obviously based on 100% completion or something rather than how far you are through the main story. Part 2 of the game is at best half the length of Part 1. Probably took about 6hrs to beat (game timer said about 5hrs but I think it resets on checkpoint reload?)
-Story and characterisation not as strong as New Blood, arguably Helga is introduced too late in the game so you don't really build up any feelings towards her (unlike say Deathshed or indeed some of the other main baddies in NO). Likewise Pippa feels underused
-Not as much variety in locations and playstyles as New Order although still pretty good for a FPS
-Escape at the start is a bit annoying, the electro gates feel a bit contrived as a way of forcing you to drop your heavy weapon
Overall it is passable but aside from the performance issues, New Order is a much better game in almost every way so I would recommend that for anyone considering this game who has not played NO.