well, MIDIface 8x8 definitely does not work standalone. Axoloti manages all routing on it.
otherwise the timing is rock solid. it's built on Ploytec GM5 chip, and it definitely lives up to its reputation — i did not expect any observable problems so far (i have it almost 2 years).
but since it relies on USB host it's plugged in, i think that bad reviews might be due to host's latencies or glitches, especially when using with DAWs that often have latency fluctuations depending on CPU load.