One thing I will say, I do get a small sense that in the last couple of months GTR seem to be *trying* to improve. In particular their comms has improved a bit, although they still seem to have a habit of publically blaming others when things go wrong, sometimes fairly but not always. Since Christmas performance has improved, and at least when cancellations do occur they to tend to be planned and communicated out a bit better now, so that at least one can reliably check before leaving home/work.
Weekday services seem to have significantly improved in the last three months or so, in my experience. I'm no longer avoiding planning around going for a GN train if there isn't a sensible alternative available (eg. late at night). My usual morning commute on the 0948 Ely -> Cambridge, about which I complained a great deal upthread last year, has been fairly reliable since about October/November.
However, their Saturday service remains lamentable. Until we get back to a proper timetable, I have no idea why they can't run 12-cars all day on the Cambridge fasts, given they're currently running a service that is inferior to what we had 20 years ago (!).
Equally, the Sunday service is poor in many respects, particularly north of Cambridge, though in that case it wasn't even planned to be improved in May 2018 (about which I complained quite a bit at the time - before lots of other things went badly wrong...)
Service recovery remains very poor too - was caught up in the power failure near Royston the Sunday evening before last, and it seems that even after the line reopened they only managed to run one train that connected into anything going north of Cambridge (goodness only knows how busy that was, as the first train in over 2 hours) - as opposed to the 5 services that should have run. They still don't seem to care about running last trains when anything goes wrong - for all their faults, in my experience FCC were quite fastidious about that. (I still don't trust them at all when there is disruption - bearing in mind the disaster at Letchworth before Christmas - and so on this occasion I went with GA instead once I knew what was going on, even though a large part of it was bus-stituted and it took ages and ages. Tedious, but I got home without needing to be taxi'ed).