I for one am happy. Why? Because from what I've heard those involved including Keanu are fans and wanna see a good movie made. Sure there is some stuff I didn't like him in, but there is stuff I did.
Aesthetically does he fit the role? Yeah. But I'm not, nor is anyone besides himself qualified to speak on the characterization and mood he'll bring to Spike. We'll just have to wait and see.
I hate, absolutely hate all this "omg they ruined it!1!", "this is gonna suck", "they should all die!" crap within what? A month of the movie being officially announced, and a day of the actors announcement? That's crap.