It's been hidden away on the NX website for a few years with no mention or links from the homepage since they dropped the "Britxplorer" name for the similar ticket.
I had been considering using one before but never got around to planning a trip. I did have a few concerns though.
It is rather unclear if the ticket can be used on demand or if reservations are required for all journeys, The text in the T&C could be interpreted either way. Obviously it is a good idea to book many journeys but routes such as Liverpool-Manchester-Leeds and the various London Airport routes and the outer ends of more rural routes would be near enough walk-up services where it would be handy to not have to be restricted to advance bookings.
As well as that it is how the ticket is presented (it appears to be issued by e-mail only) and how likely it is to be accepted without difficulty. Considering how well hidden the product is I doubt many get purchased so will drivers be familiar with it at all?
Last year I enquired in Digbeth about purchasing such a ticket and was told no such ticket exists, certainly points to them being not well known and that trying to book a journey at a station with one may be problematic.
For booking journeys online you need to use the old version of their journey planner which is also not linked from the current NX website
https://coach.nationalexpress.com/nxbooking/
Certainly the price is good, especially compared to some routes where a 7 day pass is cheaper than one return fare.