Developers who use local AI – Q4_0 vs Q8_0 KV quant?

I'd love to hear from developers who use big context windows if they notice a difference?

Obviously I would love to cut the KV cache VRAM requirement in half, but I'm worried about quality especially when we enter into 50k+ context territory.

I don't really need a full study, just wondering, anecdotally, what people have experienced.

My current setup: Docker stack with Llama.cpp server at the helm (Vulkan - I pay AMD tax daily) - 32GB VRAM, using mostly Qwen 3.6 models for development. I go back and forth beetween the 27b dense and 35b MoE. WIth a dash of the lil guy (3.5 9B omnicoder variant) for smaller stuff since it's so zippy and uses a shite-ton less vram.