In general, I think, would be totally helpful to have some built-in benchmark scene in Arnold.
And in upcoming battle of HEDT segment it would help some users with decisions about upgrade.
(if it could be stand-alone and free version, without need to launch Maya or other DCC app that would be even better)
Please consider this request, thank you.
I just posted the same question, one year later and no official test scene or benchmark data for users to make informed decisions from. =( Redshift community is far ahead in this regard.
To test Arnold properly we would need 100s of gigabytes of data, not so easily transportable.
If you want to do the Classroom.ass with some skylight and a direct and no shaders, I belive this one is floating around somewhere, but its not exactly the limit of what Arnold can render.