Playing with the Chch launch offer, I've found that clicking the cheapies referral link for didi (this is the generic random one, I'm not posting MY referral link!), it seems like different referrals give different offers. So might be worth opening a couple of times in different tabs and choosing the offer that works best for you. I've already joined a couple of weeks ago and so far saved a bunch compared to Uber (and I shudder to think what taxis would have cost me).