I'll definitely try it out, both streaming and watching. I already watch quite a bit of gaming content on YouTube and streaming performance to YouTube is a lot better than to Twitch. I can stream 1080p without any issues to YouTube, while Twitch sometimes stutters even at 480p, not even talking about 60 FPS. If you aren't partnered with Twitch, you can forget streaming at a good quality.

What remains to be seen, is how good the GUI will be for this YouTube Gaming thing. YouTube has always had a quite awful interface, to a point where I use an RSS reader to follow channels. And currently starting a stream on YouTube is needlessly complicated too, although right now it's not meant to be used the same way as Twitch.

Since Twitch banned Adult Only game streams, they will probably have a small lead.

Unless Youtube fixes their Content ID system and how it handles take-down requests, I doubt this venture will be successful for them.