1. Let's start with the easy pickings: they support linear snapshots only. What did they select to display this? Obviously not a list, but a tree !
2. Their snapshot documentation is less than 1 page in the PDF help file. Out of this, half is spent explaining how to "take" a snapshot which is probably the easiest thing they support. A quarter of the page includes a scary note about possible data loss which references some VBoxManage interface which is some script that has nothing to do with the GUI.
Also, their documentation doesn't have a single screenshot or at least pictures of the buttons users are supposed to press.
In the remaining quarter of the documentation they briefly mention revert and discard snapshot.
At no point do they bother explaining how their mechanism works, you kinda have to read between the lines what the philosophy is.
3. When you press "Discard snapshot" it actually merges changes. So you're not losing data actually, you're just losing the little timestamp that the snapshot gave you. They couldn't have picked a more confusing wording and it's not what you would expect.
4. Next to the notion of "snapshot" they have a separate notion of "current state" or "state" which is somehow related but kinda different. I'm not entirely certain if "state" is something like a placeholder that I can fill with different snapshots or just the tip of the snapshots list. Their wording makes it sound one or the other.
Also, not only did they pick such a wrong wording and show such lack in clearly explaining what their application is supposed to do, but they don't even seem to find this important. A bug report on their website complaining about this very thing is marked as minor !
I guess this is a sign of some geek mentality. They assume that people must train using the uber-software and actually read and memorize the 250 page PDF (probably at some point it all makes sense). The sad thing is that the GUI is really simple and this minimalism should allow them to focus on the details, but a third of it is broken.
Obviously I'm not talking about their "Settings" GUI where you configure the machine, that's very complex.
I'm talking about the normal GUI the users gets to see every other time after the creation of the virtual machine which has 3 tabs: "Details", "Snapshots" and "Description". The only one the user will interact for the rest of the virtual machine's lifetime is "Snapshots" and this is the one they thought it's minor. Go figure.