The U54 is squarely in the Pi competitor category. Claimed IPC is slightly lower at 1.7DMIPS/Mhz vs 2.3 for the Cortex-A53 in the Pi and this SoC clocks slightly higher than the Pi at 1.5Ghz vs 1.2Ghz, so performance should be quite similar. I certainly hope it manages to catch on and we get higher performance RISC-V chips at a reasonable cost in the future but these are clearly not it. If by "workstation class" you mean Skylake/Zen levels of performance there's a long way to go.
No, I’ve learned about SiFive from the talks they’ve given at the RISC-V workshops. I think some of those are recorded, maybe look there? I’m on mobile and it’s hard to provide a link.