I really love the X7. It's great for me, living in Sunderland. While travelling to Teesside's recent bus rally, I discovered that it took me almost three hours to get to Stockton - and that was by Metro as opposed to usual Go North East bus if I had just purchased a Get Around day ticket as opposed to a Nexus CAT ticket plus that.
Journey time if travelling from Sunderland can be halved by using the X7.

If travelling direct to Middlesbrough, I have discovered that members of the public (like me) prefer to use the X7 from Sunderland to Peterlee, and then the X9 from Peterlee to Middlesbrough. It's only ten minutes faster, but I guess people like the luxury of a 30-minute charge of their devices and prefer the safety of connections to other buses that way. Trust me - I like to take a good risk with a connection, but even I won't put my faith in the X7 to get to Middlesbrough before the OK1 departs..!