I've now been in Kings Cross, Newcastle and Edinburgh in the course of my business.
Once you get used to some of the odder features like the mad tartan and that strange table with benches in Edinburgh (illustrated in an earlier post above, are they expecting large parties to turn up with picnics?), and get used to no traditional desks to work at, they do the job perfectly well and are a huge improvement on the dingy and tired old GNER fit outs.
With the possible exception of Kings Cross none bear comparison with Euston, which is SO busy. Even then I reckon Kings Cross would be doing well to have a quarter of the throughput of Euston.
Yes, it would be nice if Kings Cross had a bar but I don't think it would sell much, so self service hot and soft drinks are fine. The old desks at Kings Cross were so small and uncomfortable that I really don't miss them. I have to admit those red leather workstation things at KX are a bit weird and, I'm afraid, rather wobbly when you use your laptop on them.