btrfs and snapperd do have a performance penalty as the number of snapshots increases. Having 100+ usually means snapper list will take north of an hour. You can easily reach these numbers if you are taking a snapshot every handful of minutes.

Even background snapper cleanups will start to take a toll, since even if they are done with ionice they tend to block simultaneous accesses to the filesystem while they are in progress. If you have your root on the same filesystem, it's not pretty -- lots of periodic system-wide freezes with the HDD LEDs non-stop blinking. I tend to limit snapshots always to < 20 for that reason (and so does the default snapperd config).

About 2 years ago I believed the same. Then I used BTRFS as a store for VM images (with periodoc snapshot) and performance went down to really really bad. After I deleted all snapshots performance was good again. There is a big performance penalty in btrfs with more than about 100 snapshots.