Recs.
Updated
SpecsUpdate
Pros
Pro Includes a Lockscreen
SLiM also includes a graphical Lockscreen that uses the theme from the login manager.
Pro Maintained Forks
There are plenty of maintained forks available, some dropped even consolekit for systemd/logind.
https://github.com/iwamatsu/slim/network
https://github.com/data-modul/slim/network
Cons
Con Abandonded
SLiM is currently abandoned, however there are many active forks some even added systemd support.
Con SLIMLOCK doesn't stop switching between VTs
But there's a solution! It works!
https://wiki.archlinux.org/title/SLiM#Screen_Lock
Con Text issues
With both Noueau and proprietary NVidia drivers have text displaying issues with Quadro M2000 and other Quadro series cards at 1900x1600 resolution - text is not visible.
Recommendations
Comments
Flagged Pros + Cons
Con Very little consistency among different versions
There have been quite some changes that break the compatibility between Slim 2 and Slim 3. Even if you learned how to work with the Slim 2, you will find that Slim 3 requires re-training.
Con Dependency injection is too weak
It is not really dependency injection, but just a configurable container.
Con Too minimal
While it's true that Slim is a microframework, it's still too minimal. When used for throwaway projects or simple prototypes, it's perfect. But in the long run, it becomes less and less useful and you end up in implementing a full custom framework in trying to tackle all the missing features.