Many people in Silicon Valley are biased against Lyft because they think that ride-sharing will be a winner-takes-all market. They are probably wrong. Once a ride-sharing company gets to a certain level of reliability and waiting times are short enough, there is little benefit to using one service over another. Uber and Lyft will both be able to claim a lead in lots of cities, and both will be around for a while.
Furthermore, if you live in a city with both, it's not uncommon to talk with drivers who work for both services.
I will also add that the need for expansion has toned down the quirkiness of Lyft from when they first out a few years back. The giant furry mustache was replaced. No more fist bumps. And the drivers I encounter are generally less talkative and charismatic. That's not meant to criticize the company, but AFAIC, there is just a lot less separating the two companies.
So playing it slow and sane might be second in the long run, but if they keep expanding I don't see them not eating into Uber's market and climbing their way up. Well, unless of course Uber's investment into driverless cars is able to come to fruition within our lifetime.