It wont be long before we have a complete Android monoculture. And that is bad.
So far RIM's BlackBerry 10 and MS's Windows 8/RT ventures haven't made a single dent in the mobile space and we do need some serious competition to keep all players fit and the market healthy.
While I'll be honest and say I'd rather see something truly free and open like FirefoxOS gain traction, I'll be pragmatic and welcome any sort of competition as good. So I have to welcome Tizen as well on general principle.
All that said... I can't really say I feel very excited about this. I've yet to see a single Tizen device. I've yet to see a single presentation telling my why this is better than what we already have. Why this is something I should get invested in (neither as an OEM, developer nor user).
It's just a name which I associate absolutely nothing with.
If they are really serious about becoming a viable third option, they really need to up their marketing effort as they're not even on the radar of the techies.
And how does that speak well of their future chances of success?