They do, but it seems a poor cousin (rate limiting, no service guarantees, only open data) of the MapQuest Nominatim service that it's named for (or is that the other way around?), which leads back to the same issues of quality vs price.

I'd love to use OSM for all the usual reasons, just asking what it's like in real life. What do the zillions of startups out there use, what are the tradeoffs you've experienced? If it were that easy an answer there would only be OSM and the commercial providers would only have value-added data.