The best thing abut YouTube Gaming is that every streamer gets transcoders. Right now I stream at 720p 60FPS I use a bitrate of 3800, on Twitch because I'm a small streamer my viewers would get buffering and lag. On YouTube gaming the stream looks great, and if a viewer has slower internet, it will auto downgrade the stream for them, preserving the good stream for archival and everyone else watching.
The problems that I see with YouTube is chat, I'm not talking about what's said in chat, that's different from channel to channel. I'm talking about the slowness of chat, and the fact that there aren't tools to make it better.
If I want to use 3rd party software twitch's chat is actually IRC based, which is friggin' great. If I want to mention someone I just type @name hit tab and boom they get my message highlighted.
None of that works on YouTube Gaming, I can't get a bot in there to use commands. etc...
YouTube gaming will be competition for Twitch, everyone seems to think that its all or nothing, or that only the streamers that currently exist are ever going to be big streams.
I'm sure YouTube Gaming will get plenty of big streamers, they may not be the ones from Twitch, but I'm positive there is room in this market for more than one huge player, and more competition means better user/streamer experience for everyone.
Lastly, the #1 reason I'm interested in YouTube Gaming, is viewers, I'm a small streamer, I only started about a month ago. I use Restream.io to stream to YouTube and Twitch at the same time. EVERY time I stream, I get more viewers in my YouTube stream than in my Twitch stream. EVERY DAMN TIME. I don't understand why, because actually looking for live content on YouTube is just about impossible compared to twitch.