I’m all for interesting side quests, but it does hurt immersion a little when High Priest Powervac impresses upon you how urgent it is that you stop The Great Finger Eater and save the galaxy, but you’ve also really got to gather nine forget-me-nots for Widow Stoop and honestly, they’re of equal importance.
The only real issue with OpenStreetMaps is that the quality varies significantly town-to-town depending on how much love it’s had by local, knowledgable contributors. Road directions are one of the more complex things to configure in OSM, especially with complex multi-lane junctions, and so densely-populated areas and major roads are likely to be quite good, whereas more rural areas can be hit-and-miss.