It's always to see other's opinion - even if it is different than ours. As a reference point we are Double Zenith and had sailed exclusively in upper suites for 24 years.
After spending 13 weeks on Apex and Edge in the past year, we have decided we will never sail on an E-Class ship ever again. I agree with you the ships are beautiful but they have some major downsides in our views. Notable the sound issues with all of the specialties dining rooms. No Walls--- open to loud Lobby with ear splitting "Light Show"
The other main issue is the sheer number of passenger in Luminae. Unlike the M and S class ships were they cook your meals to order - On E-Class the cook more cafeteria style and I have had numerous dishes that were totally inedible or cold on the outside while on a piping hot plate.
We will be taking out first cruise on QM2 in October and wont' be trying to comparing it to Celebrity but experience it as a new chapter in our life. After 24 years with Celebrity We have booked 2 Cunard Cruises, 2 Oceania, 1 Silversea and 1 Celebrity so far this year. We definitely are no longer and exclusive Celebrity Fan.
On the brighter side we just returned from 5 weeks on Solstice and love it with the exception of some small but noticable cut backs --- 1 QTips so thin stems you can't use them (had to buy my own). No Butter in OVC Grill - they have switched to little tubs of a butter blend, Butter in Luminae Cut back to 50% of normal size and Ice Cream in Luminae that was totally inedible, Icy, bad taste and texture of ice milk.