Hi there.
Corona is rendering very well in our small farm.
We have around 12 nodes (I say around because sometimes we add a node or two, depending on the needs)
An example job could be one we did recentlly (Corona job of course), the average time per frame was 21 minutes 27seconds, in a single computer with that time per frame the total render time is 125,48 hours, in our renderfarm it was completed in approximately 13 hours (started at 4:08:40, ended at 17:03:20)
The render time per frame in a 2600k was aproximately 10 minutes.
So we are not rebus (we don't want to hahaha), but if someone needs some speedup in render, think in us, we will quote your job.
I'll add that Corona is leveragin the oldest nodes brilliantly, we have some Q6600, and they are performing astonishing well, more or less 30% of a 2600k, while with mental ray they were 23/25% of the 2600k, so Corona it's awesome even in older computers.
BTW we are beckburner based, it's working fine in it's latest releases :)
Cheers!