Sipeed sent me their new SLogic16U3 USB3 logic analyzer to review(free, no obligation). Inside is just a tiny Gowin GW5AT-LV15 FPGA doing softcore USB3(!!!), which is how they made it so cheap. 800MHz@4ch is quite impressive. My verdict? Definitely going in the tool box.
They did warn me that with Windows the USB3 driver is a little unstable and can't quite reach 400MB/s(stops at 396MB/s), but so far it's been... fine? For a price of $69(nice) it's very good either way, and it should be stable on Linux/Mac.