I tend to like longer voyages, especially transatlantics, maidens, and repositioning sailings. I also look for good value when I cruise.
I picked an inside cabin with virtual balcony, which I greatly enjoyed onboard Quantum of the Seas. Unfortunately, at least most of the inside virtual balconies on Harmony of the Seas don't have the sound... so you don't hear the wind, and the sea. A bigger problem is the exposure latitude on the camera feeding the virtual balcony screen is limited, so (in particular) it looks much darker outside in the early mornings than it appears on (say) the camera feeding the in-cabin TV screen. It's also disappointing that (unlike Quantum) many of the inside cabins on Harmony don't have virtual balconies. This is perhaps one of the biggest dumb design decisions that RCL made for Harmony.
I enjoyed the main dining rooms. I recommend My Time dining, and ignore the pressure to reserve specific dining times way ahead. Just show up, and offer to share a table. You'll meet more interesting people that way (most of the time) and have much greater flexibility. Don't fail to try some of the other free venues, including Solarium Grill.
we had an inside stateroom with the virtual balcony. Had a lot of issues with the virtual balcony not working at the beginning third or so of our sailing, and the camera feeding it wasn't very tolerant of low light levels in the morning (so it looked a lot darker outside than it really was). Apparently they aren't putting the sound into virtual balconies anymore. :-(((( (Although at least some of the people on our cabin crawl said that they heard it in the cabin they visited). Cabin has a minifridge, and basically everything you need. I liked that there was a glass shower door and not just a flimsy curtain. I didn't much care for the toilet tissue hiding under the cabinet.... we took off the roll and kept it on the bathroom cabinet instead.
We stayed three nights at Hotel Californa. We went to the Chocolate museum, the Illusions museum, and the Erotica museum. All were entertaining and worthwhile.