The new route seemed to be coping well with the Christmas traffic tonight, all services seemingly running on time or with relatively minor delays. (It does look like there were some delays getting into Shudehill around 3-4pm though. Since the new route came in traffic around Victoria/Printworks can be a problem)
Meanwhile there were long delays to all services using Deansgate and John Dalton Street. The traffic on the old route was just silly last year, so I think at this time of year at least the new route is definitely better.