I switched from Nixos to void Linux. Here's my experience so far.
I hopped from arch (2010-2019) to Nixos (2019-2023). I had my issues with it but being a functional programmer, I really liked the declarative style of configuring your OS. That was until last week. I decided to try out void Linux (musl). I'm happy with it so far.
Why did I switch?
Nix is extremely slow and data intensive (compared to xbps). I mean sometimes 100-1000x or more. I know it is not a fair comparison because nix is doing much more. Even for small tweaks or dependency / toolchain update it'll download/rebuild all packages. This would mean 3-10GB (or more) download on Nixos for something that is a few KB or MB on xbps.
Everything is noticeably slower. My system used way more CPU and Ram even during idle. CPU was at 1-3% during idle and my battery life was 2 to 3.5h. Xfce idle ram usage was 1.5 GB on Nixos. On Void it's around 0.5GB. I easily get 5-7h of battery life for my normal usage. It is 10h-12h if I am reading an ebook.
Nix disables a lot of compiler optimisations apparently for reproducibility. Maybe this is the reason?
Just a lot of random bugs. Firefox would sometimes leak memory and hang. I have only 8 GB of ram. WiFi reconnecting all the time randomly. No such issues so far with void.
Of course the abstractions and the language have a learning curve. It's harder for a beginner to package or do something which is not already exposed as an option. (This wasn't a big issue for me most of the time.)
For now, I'll enjoy the speed and simplicity of void. It has less packages compared to nix but I have flatpak if needed. So far, I had to install only Android studio with it.
My verdict is to use Nixos for servers and shared dev environments. For desktop it's probably not suitable for most.
I also haven't noticed a significant performance hit from using nixos on desktop coming from arch a few months ago. Nix definitely does a lot of stuff and that can chew through bandwidth at times, but overall I think the time saved from not compiling heaps of aur packages has outweighed the time lost to nix updating and maintaining the overall state of my system on every update.
I tend to run relatively lightweight systems these days and haven't really noticed sluggishness compared to an equivalent system on arch. My desktop environment has been sway on both for a while and this may account for my experience of a leaner and more reliable system on both, but it's hard to say.
I'd definitely want to investigate bandwidth optimization strats for nix if I was heavily constrained in that area, or possibly move to something where cpu and bandwidth constraints were given priority over reproducibility. For my current setup nixos has been a game changer on both desktop and server, but I only really have arch as a direct comparison.
( For context, my current desktop nixos systems are a 9 year old low-end cintiq, a 2017 dell optiplex 7050 minipc, and a steam deck. They all have ssds and at least 12gb of ram. All feel super snappy for everyday work with a web browser and a heap of open terminals and workspaces. )
Thank you that makes sense. When I get my hands on a more powerful machine and have less data constraints, I'll try Nixos again. I do miss it sometimes 😆