My experience has varied a lot. I've dealt with 3 different dealerships (1 in CT, 2 in So FL). None were dedicated Genesis dealerships. The CT dealership was an hour away, but they provided concierge service leaving me a brand-new Genesis loaner. They provided maintenance and a warranty repair (rear hatch latch was faulty). They had my car a couple of times for one day each. They communicated promptly. One dealership in FL provided maintenance (oil change, etc), communicated promptly and left a loaner. They had my car just one day. The other FL dealership was a disaster, had my car 48 hours for an oil change and tire rotation, could not provide me a loaner, and made me pick up the vehicle when it was completed. Communication was awful. I sent a letter of complaint about them to GenesisUSA but I'll never go back to that dealer for anything.
My sense is that it is difficult to make generalizations about service. Two out of three experiences were good or great. But it is a good value. No charges for anything. Yes, Lexus was better service but frankly I like the Genesis better than my Lexus as vehicles go. And Mercedes charges a bundle for anything. Jag and BMW are not as reliable as you would think. I've had them all.