The basic idea seems to be that you create links to all your dotfiles and the actual files are all kept in a single directory structure, presumably for easy sharing with, for example, git.
It seems that rcm has a few interesting features.
It gives you an option to have host-specific dotfiles, which is very handy when you're working on multiple (types of) system. My laptop doesn't always have the same needs as my PC and my server(s) definitely have different needs.
In the short time I've spent with it, I've also found a few things I don't much like.
Everything in a single directory
I'm not so sure about the choice to put everything in a single directory structure, which top-level dotfiles in the top-level directory. This links all the files together in a repository-idea kind-of way. I can't have a zsh repository and an Emacs repository without also having different rcm source directories.
Actually, this isn't entirely true. I can still separate them, with the use of labels, but not in an ideal fashion.
Unfriendly to directories
It doesn't seem to like linking directories, though it can. Linking
directories is essential for me as I can on occasion remove a file
from one of my configuration directories and I don't want to have to
keep track of dead links like that manually. If you do link a
directory, instead of it showing up in
lsrc as a single entry, all
the files in the directory are shown separately.
The labels are a nice idea, but they aren't what I expected them to be when I read the description. Like host-specific dotfiles, labeled dotfiles are put in their own directory. This allows you to separate the dotfiles from others. What I didn't like about this implementation is that afterwards you always have to specify which label you want to use, which seems to make it impossible to still setup your dotfiles in a single command.
I personally won't be using rcm to manage my dotfiles. The solution I have right now with GNU Stow works better and is easier to setup, although that too has its drawbacks.
This is not a definitive description or review of the software, I have spent only a small amount of time with it and these are the findings I made when trying to set it up with a few config files. If you really want to know about it you should try it, it has quite a bit of documentation to get you going.