Re: Oh, Snapcraft!
For packaging desktop apps, it's probably fine. System tools, not so much.
As an example of snap breakage, have a look at what happened to lxd in the last couple of weeks - and it's not the first time lxd has broken in this way.
People following the lxd "stable/latest" branch were auto-upgraded to 5.21 (note "stable" in that channel name). That upgrade removed the zfs-0.8 userland tools; snaps have to carry all their own binaries and libraries, rather than use the systemwide-installed ones. This broke anyone using lxd with zfs storage running a kernel with zfs-0.8, which includes Ubuntu 20.04 with its default kernel, and Ubuntu 18.04 with HWE kernel.
So, just rollback the snap to 5.20 then? No... at the same time they also made a change to the lxd database schema, which is applied on 5.21 upgrade and is irreversible. Oops.
The solution for users on Ubuntu 20.04 was to upgrade to the HWE kernel and reboot, giving them a kernel with zfs-2.1. Canonical also released 5.21.1 which reinstated the zfs-0.8 userland tools - and retrospectively nominated it as an "long term support" release (more stable than "stable") - which means that Ubuntu 18.04 HWE is now also fixed.
However, this caused breakage across the world, and it wouldn't have happened if lxd were still packaged as deb packages: the deb packages declare their dependencies and are built to run on a particular version of the OS; and it would have been using the zfs tools which were installed on the system, and which matched the kernel in use; and they wouldn't have been silently updated in the background by a *daemon* trying to be your auto system administrator.
As it happens, there's another issue in play here: last year Canonical decided to take lxd away from the linuxcontainers project, and subsequently changed the license and required a CLA from contributors, so linuxcontainers made their own fork called incus (by the primary developer of lxd, who also left Canonical). This is all nicely packaged up as a proper deb package. As a result, by migrating from lxd to incus, you can de-snap your life - whoohoo!!
Debian had actually imported a deb-packaged version of lxd, but they are planning to abandon it now in favour of incus.