What do you find difficult about it?
For the little while that I sometimes used Hg I found it much easier to get my head around.
It's mostly a lack of practice/use.
Shared windows mount
Visual Source Safe
CVS
SVN
Perforce
ClearCase
Git
Team Foundation Server
They called it "multiple checkout", and the manual strongly recommended you do not turn it on.
The software had issues with corruption due to operations not being atomic.
It was literally less functional than copying to a shared drive. Of course management and other developers refused to believe that OSS solutions were better, MS ecosystem developers were an extremely insular group.
Incidentally, I remember one person at Microsoft who claimed to be involved in the decision to adopt sd circa 1999 saying that Microsoft has the right to turn sd into a product if it so chooses. (He/she was responding to contrary claims made on an internal email mailing list which was very widely read, so I assume if he/she was misremembering or lying he/she would have been called out.) Though ultimately MSFT made VSTS/TFS version control instead, which has striking resemblances in concepts to sd/p4.
dunno, I like git better, but at the time it did what our small team needed. Granted, we always ran into issues with one of us having a file locked that someone else needed, but onboarding was a breeze.
I'm glad I use git now, but Sourcesafe was an okay introductory source control solution.
When I was your age we used RCS and SCCS, in the snow, up hill, in both directions. :)
Seriously, I have no doubt git has an awesome on-disk format, but whenever I use the git(1) command I want to slit my wrists. I'm sure if a developer uses it many times a day it's possible to get used to it, but as a sysadmin that only uses it sporadically, I basically do:
* git clone
* vi repo/some/file/blah
* git add/commit/push
* rm -rf repo/