Has anyone here tried the revB? Are there any actual differences or improvements vs. the original?
I doubt that anyone outside SiFive without an NDA has one yet. Mouser says they are expected to arrive Jan 22, 2024. But you can learn some info by looking at the Getting Started Guide and schematic changes.
There is a new auto-restart DIP switch and associated circuitry. That is useful for anyone that wants to run it as a server, and doesn’t want wire up a remote control relay to do the auto-restart that the original board needs. There are two headers for chassis fan control. That avoids the USB powered fan that the original board needs. There is a jumper for RTC frequency control that may not be useful to anyone outside SiFive. There is a power regulator that has changed to a different part. There are some misc minor resistor, capacitor, diode, transistor, and jumper changes. Otherwise, it looks like the same board. Some of the ICs on the board might be newer revisions of the same part. That kind of info isn’t on the schematic. But it looks like the exact same SiFive CPU as the original board.