I have 8gigs of RAM too, and rendering via Luxus uses around 2 of it (well, add another 2 if you leave DAZ Studio running too, but that's a given).  The issue seems to be that it hogs too much of your CPU. 

***** When I'm rendering via Reality... CPU will run around 85% with 2.1GB RAM used.

***** Identical scene via Luxus... CPU will run around 95% with 1.9GB RAM used.

Via Luxus, I can't use my PC for anything else while rendering or it will crash (blue screen of death) which I think is due to using too much of my CPU (i7-2600K @3.4GHz)... this is after latest Luxus update (before that it would crash after rendering more than an hour or so even without using PC for anything else, so I'm sure it's something they'll continue to try and improve upon).

Via Reality, I can browse the internet, watch videos, do artwork etc etc all without any significant problems.  There's even been a couple of times that I'd forgotten to stop a render that was "done" and had started rendering my next scene... sure my PC did slow down and get sluggish (that's what made me realise a couple of renders were running at the same time), but it never crashed.

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I hope Luxus continues to improve and become popular, as so long as there's a level playing field, there's room in the marketplace for it and Reality.  I'm willing to support both Luxus and Reality, especially as I see it as a potential tool to add to my toolbox rather than a replacement of Reality.

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Incidentally, I have noticed a few comments that Luxus handles default DAZ material settings than Reality - this is true up to a point i.e. results look like 3Delight renders despite it being Luxrender.  Attached is a Luxus test render I did using Danae's Dublin texture - it doesn't look bad so long as you don't know how same texture can look when set up via Reality.  You'll probably also note the transmaps on the hair have a bit of an issue too, which will hopefully be addressed in due course.

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