Well, for playing games I use the flatpak version of steam and it works OK.
For dev work, it’s great overall. Especially its ability to create separate reproducible environments with whatever dependencies you need for every project. However, there are some tools (rare, but they exist) that don’t work well with it, and if your dev work happens to need them, it can becomes a problem.
For day to day (i.e. web browsing), it works the same as anything, with one disadvantage: there is a disadvantage here: it downloads a lot more than other distros on update, and uses more disk space. The biggest difference between NixOS, and say Arch, is not how it behaves once it’s up and running, but in how you configure it. Specifically, you have to invest a lot of time to learn how, and set up your system initially. But then reinstalls, and (some of) the maintenance, become easier.