You can never go wrong with more Jesper Kyd (I really hope they can get him back for Darksiders III).
Nightwar is definitely on my wish list, but my backlog has grown too large recently, so I didn't feel ready to pick it up right on release. But I've heard mostly good things about it (though I'm not sure how great the Mac version is; it's Unity, so my guess is "good enough, but not too good").
Yeah, I was just like "nah, I have Windows for that".
I mean, I guess it's great for people who don't have that option, but honestly, I think Nvidia should just concentrate on improving their drivers (none of the recent Metal games can even officially support NV GPUs) and then make Apple an offer it can't refuse to get their hardware back in the Mac.
I'm not convinced that this service would do anything other than further marginalize the already marginalized Mac games market. It's basically Transgaming 2.0, now with no effort whatsoever required on the part of the game's actual developers (or rather publishers).
I think the greatest chance for it to shine would be allowing Mac users to play legacy games that will realistically never come to any other platform (but I'm not sure how much support the service will offer for decades-old games).