On a date not that far away (before the end of the current football season!), if you used to have services via London Bridge to Charing Cross, the planned service pattern suggests you are more likely to have direct trains to Luton Airport than to Peterborough.
My journey from Holborn Viaduct didn't change in either speed or frequency when it switched to City TL, but now the train is already full when I join it instead of me getting first dibs at the terminus. And electrification of the main line out of Kings Cross means I lost the direct trains I used to use to visit my family.