Once they link up the various sections, it will be a big winner. Our London family are on the overground that runs down towards West Croydon. Being able to get to/from LHR with one change at Whitechapel (where there are lifts and escalators and moving walkways) is a great improvement to now. Normally its HEX or overground to Paddington, tube to Whitchapel and change again, or Tube from the airport to Green Park, change for Canada Water and then change again. Anything that involves the tube and suitcases is generally a nightmare.