This is a Trip Report from the Premium Economy cabin
Ground Staff
Food & Drink
Entertainment
Seat
Cabin Crew
I checked in the day before only to find that for some reason the seat reservations on our DL flights had been wiped, and the only seats available were not together. As the SFO > SEA flight was so short we decided not to worry and ask if it would be possible for us to be seated together when we arrived at SFO.
We drove down early on the morning of our flight and were a little later to arrive than we'd hoped as traffic was fairly bad. We arrived at check-in and were ushered to the Premium Economy check-in desk which wasn't too busy. The lady there was very friendly and kept extolling the virtues of the No. 1 Traveller Lounge as we didn't have CH access. Not sure if ground staff have been told to push this, but she kept saying we were eligible for free access. I didn't think this was correct so didn't ask anything further, but perhaps should have asked for clarification. She printed out our boarding passes for both the VS leg and the DL leg. I didn't check the DL ones--my mistake, as I will explain later!
We were through security in no time at all (we have it down to a fine science, now) and had sandwiches and drinks from Pret in T3 as there was only about 40 minutes to go until boarding. Our boarding passes were stamped priority, so we got to skip the long queue to get into the gate. Once in, they also let PE board before Y, which doesn't always happen, in our experience.
We love PE as a product as we find it a good mix of comfortable and affordable. Our seats on the outbound leg were a little tired, and reclined a bit even if you didn't press the button! Overall they just felt a bit rickety. But, regardless, they were very comfortable. Our cabin crew team were fantastic. Sadly due to their badges flopping down and the pinafores being in the way I couldn't make out their names (I should have asked, I know!) but they really did make the flight. They were really fun and bubbly and exceptionally helpful. When they brought around chocolates my OH was asleep, so they left him an extra one and we joked that it might not last... thirty seconds later one of the CC snuck back to my seat and gave me an extra chocolate!

The flight was fairly standard, in a good way. Drinks were offered as soon as we boarded, the in flight meal was served promptly and was pretty decent. I can't remember what the veggie option I had was, but it was quite tasty. I left the dessert as I found it too sweet. I watched two movies and the IFE worked really well throughout. I took them up on some sort of pastry snack part way through the flight. I really should write this stuff down so I remember it better for everyone reading... in the meantime, you'll have to put up with my vague food descriptions. Sorry! I then tried to get a bit of sleep for the remainder of the flight. We awoke for afternoon tea which I passed on as I wasn't too hungry. It was at this point I checked our DL boarding passes for our connecting flight and noticed that whilst my husband had been assigned a seat, my boarding pass just said "GTE". I was a bit worried about this and asked the VS CC if they knew what that meant... none of them had seen it before and all we could surmise was that it meant I needed to enquire at the gate.
We landed in good time and disembarked quickly. We had a short wait (maybe 15 minutes) in line for immigration as we managed to beat the hordes. I like SFO airport as the staff there are always quite friendly, so even going through immigration is reasonably pleasant. We had to go through the rigmarole of collecting our bags and clearing customs before re-checking them, but honestly it was incredibly painless.
We then made a beeline for the Delta desk to ask about my ticket. The lady we spoke to initially seemed really concerned and spent about two or three minutes frowning at a computer screen before disappearing with our tickets. We waited for five minutes, which doesn't seem like long, but felt like a REALLY long time! When she returned, we were assigned seats (phew!) but not next to each other. No big deal for a two hour flight

Onboard it transpired the seats we were given were economy comfort (thanks, Delta lady!) and there were a few no-shows, so we got to sit together after all for the remainder of our journey.