Overall the Raspberry Pi Zero does not feel slow when using the command line. Sometimes you see a bit of delays but overall it is pretty responsive.
One notable exception is updating the system (or installing a large number of new packages). Even though downloading is as good as any other Arch Linux system I own, the installation of the packages tends to stall quite a bit (especially when updating the man page index). That is mostly due to the SD card since they don't offer the best I/O. I have the same problem whenever I install Linux on a flash drive. Updating is incredibly slow due to the limited I/O of these cheap flash devices.