NLS is shocking to my ears in a good way. It's a DSP hog, but it has much better sound and drive on the channels as well as the best sum plugin I've heard. Because of the DSP weight, I tend to wait to start using it until everything is arranged so I can start freezing tracks (I use Logic).
My favorite settings are the EMI and Neve. I don't normally mix different channels because it seems to work better when the same make is used on all strips, but I often use a different bus brand with another brand of channels. Basically, just use your ears.
NLS makes me wish I was working on the latest 12-core Mac. It definitely taxes my laptop CPU, but it's worth it. Beats paying for an outboard sum box and totally delivers on classic console sound, in my opinion.