My husband and I had our gay honeymoon (following our civil commitment cermony) in Naples last month and to be quite honest after sightseeing and climbing volcanos, trudging around Pompei and shopping we were too tired to seek out the scene. I believe it is quite a small scene but interesting none the less.
Make sure you eat pizza which was invented there but don't expect to enjoy another one after you return home, you haven't eaten pizza until you have eaten one in Naples. The locals won't eat rubbish so everywhere serves great pizza.
We stayed at the Excelsior on the seafront which was just superb. Very grand in an old European style. They even uprgraded us to a five room suite because it was our honeymoon, although more likely because I am SPG Plat. We did tell them what the occasion was though so who knows!