Assuming that Didi didn't have the resources to expand into the US directly (and god knows Lyft isn't going into China any time soon), I think this is a great deal. It allows Didi to maintain a reasonable modicum of pressure on Uber and dip its toes into the US market without any significant resource outlay. It doesn't though help Lyft to compete with Uber any better than the somewhat lackluster job they've done of it in the past couple of years. Perhaps the money, and the advertising it allows, will help. There is still a significant proportion of people who have never used Uber or Lyft, what the companies do to capture them is going to be very interesting.