I've been out and about on the recently changed services in Newcastle, and this is what I saw:

51 - The link from north Whitley Bay to Newcastle isn't really used, but the services is quite busy for local journeys. I rode the service from Newcastle to Whitley Bay and it was busy from Newcastle to Wiltshire Drive, then quiet to ASDA, average from ASDA to Shiremoor, quiet from Shiermoor to Newsteads Drive, and average the rest of the way. It is allocated Solos.

52 - Not a busy service at all. I was the only one on from Killingworth to Four Lane Ends, but a few got on at Freeman Hospital. It is allocated anything, but mainly B10BLEs.

54 - This is a very busy service, especially Killingworth to Whitley Bay. The service left full from Killingworth, and it was well used the rest of the way. The Killingworth to Newcastle has average passenger numbers. It is usually operated by Pulsars.