I am a paraplegic and my wife and I are regular cruisers with Celebrity, but this was our first cruise in a Solstice class ship. We recently sailed on the Celebrity Equinox on their Ultimate Caribbean itinerary, in Aqua class.
We have found Celebrity to be very accessible for wheelchairs, with a few problems here and there, but there have been major improvements with the Solstice class. One of these is the gently tapered ends of the ramps to the dock in the ports. It used to be that the ramps always seemed to have a sharp drop off at the ends, the ends were tapered, but very steeply, so that one was always concerned about slipping off the wheelchair seat, I usually wear a wheelchair belt to forestall this possibility.
Another major improvement is the ease now of going from the interior unto the promenade and pool decks. The double automatic doors open quickly and the ramps over the doorsills are very gentle and now cause no problems, which is nice for a change. And these double doors are all over the ship now, rather than in just a few selected areas. In fact when we were traveling from one end of the ship to the other, we found it was fastest and easiest to go through the doors and use the outside promenade on deck 5.
Lots of room, and right across from stairs leading directly up to Aqua Spa (handy for the spouse of the wheelchair user)