Mrs Greenback and I would certainly find the railcard useful. This year we have udnertaken plenty of journeys together, visitng London, Southampton, Cardiff, Bristol, Leeds, York, Scarborough and Carlisle. Once we had bought the railcard, we would be tempted to make more leisure trips, increasing revenue for the railway. Wjtjer this additional revenue would work out as more than the money we had saved by using the card is debatable, as we never drive for long distance journeys and because of work the extra trips we would make would be shorter distance ones (though perhaps not necessarily that much cheaper of course!).
That said, I have concernes because I think it would be preferable to have a proper national railcard that could be used off peak by individuals, who could take others with them, like the Network Card. I would alos prefer a much simpler fares system like that in the Netherlands, and I don't realistically expect to get either of those things very soon, but I do think there will be elss chance of achieving the former if this scheme is deemed a failure.