Curb (TaxiMagic) is just a (bad) dispatch-management service; it's not really built into any taxi system, and doesn't provide any sort of feedback or quality control on the ride experience.
There is a feedback mechanism in Curb (I'm a former employee). For some taxi companies, LA for example, Curb has very deep links into the dispatch system and can choose not to offer rides to certain drivers directly - so enough bad feedback and the taxi driver will no longer get Curb ride offers. For other taxi companies reviews get reported back to the taxi management and they can act on the report as they choose (some companies act quickly and promptly and some others don't do anything).
They are succeeding, but not to the extent of Uber/Lyft. Regulated taxi industry pricing is much higher than lyft or UberX pricing. If taxis get de-regulated and/or UberX/Lyft get regulated then Curb/Hailo/etc will be well positioned.
> Regulated taxi industry pricing is much higher than lyft or UberX pricing.
Empirically, it's a bit higher, but not much. A few data points from my recent experiences - I take a cab to work once or twice a week if I'm running late. The last 3 Ubers (UberX) I've taken were $11.02, $11.45 and $9.79. The last 3 Hailos I've taken were $12.29, $10.39 and $12.09. These are from similar times on similar workdays with similar traffic patterns. (Edit: this is in NYC and the Hailo fares include a 20% tip)
I'm thinking I'll pay the extra dollar from now on, worth it to avoid supporting these business practices. Although my biggest problem with Hailo has been availability - it's often impossible to get a Hailo near rush hour while Ubers are always available.
I suppose it depends on where you are using the services. In Los Angeles, after you factor in tip for a taxi driver, Uber and Lyft are about 40-50% cheaper. Here's Uber's analysis of the pricing in LA http://blog.uber.com/LAuberXpricecut
Uber controls its fate, though its success may be stymied by municipalities. Taking the business directly to cities puts the onus on them- a much harder proposition than providing a good service. I know which business I'd rather run.