I agree with you completely about making the cold brew separately so that you have some on hand! Other reason is that I very much prefer the drip method of making cold brew as opposed to the infusion method. Just seems that much smoother to me.
While I have not had the cascading effect to the full level of a commercial coffee house using a true stout type tap and N2 vs N2O ... I do get somewhat of a cascading effect and I actually do like the slight natural sweetness of the N2O! Just keeping in mind this is a home version of a commercial thing ... I have been very pleased so far.
I did find another source of the 16g N2O cartridges at bestwhip.com ... They are about a third of the price of buying them from Growlerworks ($5 per box of 5 vs $15). I used one of the BestWhip cartridges yesterday and it worked just as well as the ones that came with the uKeg Nitro.
Coffee preparation techniques besides espresso like pourover.