When going from light to dark, the preview will constantly flicker. This can't always be replicated and is maybe a memory issue.
When post-process is turned on, selecting a prop will create a ghost image. This ghost image persists even when turning off post-process. The only way to remove it is to completely restart Hammer.
Physics simulation seems to crash more often
Texture browser is magnitudes slower, more prone to crashing, and always "tears" while scrolling. (If it's GPU accelerated now, this is much less reliable on my end than how it was before.)
QOL things:
Model browser doesn't keep searching after being closed, so you have to keep it open to load all assets. A little tedious when dealing with crashes.
"Recent files >" is neither 'recently opened' or 'recently modified' but a secret third thing that I can't figure out. Either that or it's not persistent between loads.
The new accurately-sized preview for textures makes it hard to identify what some textures are.
Animated props from a new version of Source (ex. INFRA assets) register as corrupt and result in an instant crash. Understandable that they're incompatible with Hammer++ but it would be nice if there was a way to simply not preview the model, or close the model viewer instead of crashing the entire program.
When using Sprinkle and with "Random Yaw" and "Align to Normal" both turned on, the prop first aligns to normal then gets a random yaw, resulting in props sticking out of the ground. This makes it harder to place rocks and foliage, and could be fixed if the order were reversed (random yaw first, then aligned to normal.)
QOL things: