In true YD style, I am going to explain my POV, even though I don't meet Brian's criteria of having dived to 'those depths and therfore not capable of having an opinion that is valid.
The reason I haven't (yet) dived below 48m in the UK is because I will readily admit to narcosis and I won't go deeper until I can do the depth with a clear head.
I have an instructor who would quite happily do my ER course, but I am waiting until such time as I can do a trimix course. Until then, I wouldn't dive deeper than about 45m ish.