Using the JH7110 chip they are starting with, somewhere around the last Pentium 3s and PowerPC G4s, but quad core instead of single core. And 64 bit. So maybe the closest comparison is the original Core 2 Duo MacBook Air, which ran at 1.6 MHz (for about 4 seconds before it throttled to 1.2 GHz, which the RISC-V shouldn't do).

Or, in the Arm world, a bit slower than a Pi 4, but a lot better than a Pi 3 (especially because 8 GB RAM and PCIe/M.2 not 1 GB and SD card).

I'd expect a 2nd generation motherboard fairly quickly. If it comes in the next six months (Eswin EIC7700) then probably about the speed of a mid-range Core 2 Quad. If mid next year (SG2380) then early i7.