Biggest problem with 1.9 is that its going to take at least a year or longer for mod developers to update their mods.
Also am I reading this correctly? Shaders are going to be a default function of Minecraft now? That would mean the shaders mod is irrelevant and no more Forge would be needed to just run shaders, though I do find optifine a necessary thing due to how Minecraft performs even on a high end machine, I blame java.