I am still playing with mine, but it easy to make it work with 300 gr slug. So far brass has been good. The only down side I found is there is a lot less data out for it, but quick load helps with loading data.
I continue to consider it as my next rifle (my 277AM has the Lapua bolt face). My only concern continues to be the availability of their brass. It is hard - and sometimes - impossible to find. To my mind, if Norma wants to promote this new round, they need to do a much better job of getting their brass out there to the public. 338 Lapua brass is usually in stock at no less than 10 retailers on the internet. 338 Norma only has 3-4 souces that I have been able to find - and they are almost always out of stock. Even gunsmiths that have the reamer will only part with a 100 pieces of 338 Norma to get you started. All this tells me that supply is not caught up with demand yet. Although I would like to try this new round, I will take a wait and see approach. If things don't improve drastically in terms a brass availability, I will go with the 338 Lapua.