I cringed every second he was on screen. While it was clearly better than any CGI character I've seen, it was still strikingly obvious, especially as the editing cut between CGI-Tarkin and real-human Krennic.
The textures are superbly detailed, but Tarkin comes across as a botoxed-up; there's something very wrong and jerky about the movement of his eyes and mouth. There's also something horribly wrong about his skin colour. In the film he looks like he's deathly ill — reddish eyes, deep purple eye sockets. Cushing was elderly in the original trilogy, but he wasn't near death.
I don't think it's a coincidence that you (or, rather, I) can't find a single clip of the CGI Tarkin on YouTube. I did find a low-res cam screenshot [1], and you can see the uncanny valley even there. He looks a bit vampiric.