Thanks Tom, although to me it just looks like there is more noise in the V5 version which would ultimately clean up eventually and look VERY similar to the result of the V6 image? Or am I not seeing something? Whilst I can see the obvious difference in terms of how cleaner it is in a quicker time, the difference in 'realism' isn't quite enough to wait all night for a render on the off chance it has those artifacts, which are way more obvious than the increase in realism :)
I must admit though, when I've had it off, I've not gone back to using portals, simply just turned it off. I'm probably not noticing time savings as I tend to run renders over night as a lot of studios do (well the ones I've worked for did), which is why I'm looking for the realism boost element to it. Without question I'd use it if I could guarantee not waking up to those squares, but you don't always spot them when using IR or regions when developing a scene, and it's only when you come to look at the final render (usually on deadline day) that you actually spot them