I don't think The Valiant Ones is nearly as good as the more well-known King Hu films out there, but it's definitely not terrible. I wasn't crazy about it, but that might be a consequence of getting the hang of other kinds of martial arts movies and not really remembering how King Hu's felt. I think you really have to be in a certain mood in order to slip into them properly, and The Valiant Ones wasn't quite doing it for me today.
It looks and sounds nice, and the action at the end is exciting. Before then, I did find it to be a bit plodding and it felt longer than 102 minutes... it was either hard to follow what was going on or hard to care; maybe a bit of both, but the technical qualities of the film and its bursts of action made up for that somewhat.