The only spanner in the works is for those living in south London.
That 0740 from Charing X leaves London Bridge at 0750. The journey on the Northern Line of the Tube from London Bridge to Kings Cross/St Pancras is about 20mins.
So if you live in north London, it's great, if you don't, it's busines as usual. Unless they scrap the old service and make you use the "faster" and more expensive service, in which case you get screwed.