They are doing ok right now. I use West Anglia, the timetable is OK, it just about works, lots of small delays but no major issues, and the exGN 317s have clearly helped, lots less shortforming, and no 4 car shoulder peak diagrams any more, and has allowed 2 x 12 car diagrams on StanExp which is welcome.
But, got to remember they have run basically a steady state franchise for many years. We will find out how good they are next 12-24 months as trains replaced and timetable reworked.
I am sceptical - Brantham is late/not happening, franchise agreement commitment to ensure 12 cars trains can stop at Hertford East, Wickford, Manningtree, Kings Lynn, Elsenham, Ware, St Margarets and Enfield Lock Stations by 1 Sept 2018 will be probably be missed, and SDO on 317s and trackside beacons by 31 October 2018 also looking tight.
And we haven't seen any proposed new timetables yet either. May 2019 Hertford East goes 3 TPH off peak, STAR starts and Norwich Cambridge extended to Stansted A all day - should be doable. Its the May 2020 TSR 3 which looks very challenging.