I got to fly on ship 7, DL121 earlier this week and really enjoyed the DLOne Suite.
I was not expecting the suite to be as roomy as I thought (in fact I thought it was going to be tight like the DLOne 763/4 seat) and appreciated the abundance of storage spaces to place objects, including that cubby hole for my shoes and the DLOne slippers. I was able to sleep on my sides, and even on my stomach very comfortably. At the end of the flight I concluded the suite is far superior to the UA Polaris Seat and NH's Business Staggered seat - far superior (loyal UA/NH customer here). Call me old fashioned, but the suite and entire reconfiguration will be received better in the 777's than the A350's. You can use the more spacious (vs the A350 lavatories) two lavatories near the entrance to the cock pit, or the other two lavatories near doors 2L/2R which I think are for Premium Select.
You loyal DL customers should be very pleased at how DLOne is progressing.
I personally just wish they would return to GUM again so that I could try the Suites again (A350 flying NRT-SEA route in March).