We have just stayed here for a week, combining a few days by the sea and a few days visiting Rome.
The hotel is clean, comfortable and well kept, and the staff are generally helpful and friendly (except at checkout, when we had an early train to catch, and the guy on checkout was far more interested answering the phone).
Nettuno itself is OK, but it's not a pretty town. If you're expecting something ridiculously cute like Sorrento, think again. Also, if you’re not a lover of fish you might be a bit challenged finding something to eat in town. If you do want to combine Nettuno with a Rome trip, the train to Termini takes about 70 minutes, runs hourly, and costs 7 Euros for a day return including metro and buses in Rome. Last train back is 21:47, so don’t expect any late nights in Rome.
My one piece of advice would be if you're staying over a weekend, try to get a floor on a higher floor. The road outside can get quite busy with traffic and pedestrians. If you like people watching, it seems like the whole town dresses up and promenades each evening over the weekend.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC