We've been on the Westerdam five times since December 2013 all mostly the same itinerary! We love the ship and are very sorry to hear it will no longer be in the Caribbean in the winter. We cruise each December to get away from the cold Appalachian Mountain winters!
As a treat we accepted the paid upgrade to a Neptune suite and we were not disappointed. The suite was very large (before we always had Signature Suites - also large!). Also you get to board first if you are a Neptuner! That was great - we always arrive at the beginning of boarding - more time on the ship! We fly into FLL the night before.
We were greeted with a bottle of fizzy wine and water. The usual high standard of the cabin attendants goes without saying. They were happy to work around our schedule to service the room.
The Neptune was a treat - we normally have Signature Suites. It is a HUGE cabin with a separate "dressing area" with mirrors and a small seat. The bathroom is pretty much the same as the Signature Suites. There is a separate bath (with Whirlpool) and shower. There are also two sinks.
In the room was a new Bose sound dock that was very good - will miss them on our normal cruises.
The Neptune Lounge was very good and the attendants were very helpful - they helped us order dinner in our room one night! The lounge has nice food "nibbles" each day which are changed about three times a day.
We did not use the free dry cleaning and other services of the Neptunes, but they are really nice suites with HUGE balconies. I'm not sure I'd pay full price but if you get a good deal on upsell upgrades I'd take it! Splurge!