I think the big thing was the slipper clutch. Personally, I have not had any issues with my '14 N1K and the clutch. But many have said they have and converted to the slipper. The reviews are all positive on the slipper clutch. When I need a new clutch, I'll go that route. For now, mine works fine. If you have a 2015, enjoy it. Not enough difference to matter. I love the black/grey scheme by the way. My only beef with this bike in general is the lights. It should have halo's with projectors as standard. I hate riding at night on it. Other than that, best bike I have ever owned. Hope you feel the same.