Playing on this new ZS felt really good and it made me miss when I played on the server. The only major complaint I have that I can remember is hitting players as a zombie not registering when I hit players or try to launch props as a zombie. I'm sure there are technical gmod terms for this but I don't know them. When I try to hit players while both of us are moving most hits miss even though I'm close to the player and aiming at them. When I prop hit I was able to move and jump after clicking on the prop and it would still count as a hit. Now I have to stand completely still and it's not that accurate either. Things like this really detract from the experience for me and is frustrating especially since I'm so used to the old style.
Another complaint is buying weapons as humans. During matches, I can hardly afford any gun barely even a crappy SMG because most of my SP is spent on ammo so I can keep killing and medkit charge when I'm a medkit. I mostly end up using a Glock or Deagle throughout the whole the game and the only time I primary weapons is when someone dies and I take theirs. I'm not sure if weapons are too expensive or you don't earn enough SP from actions such as killing zombies and providing ammo and heals for players.
I like the HUD. It's very simple and looks nice. I noticed some issues with the howler too but I'm sure you know that. This is all I can remember from my recent experience testing the new ZS.