I flew a bunch of these, and am happy to help out.

China Eastern is mainly used for Delta fliers to MR status: all their revenue fares earn 100% MQM as a "Tier 1" Partner.

China Eastern is an attractive choice because of their rock-bottom fares in both Y and J. Their fares are extremely cheap, and often given values of 1-3cpm, particularly for North America-Asia fares with connections.

Delta MQMs:

You earn 100% MQMs per mile flown on all fares, and typically the long-haul flight is in the discount economy fare class. However if you have any connections within Asia, sometimes these will be a higher fare class, including B and Y. These earn 150% MQMs and are calculated separately.

Delta RDMs:

You earn based on distance. Until Jan 2018, it's 30% for T, and then 25% after (cheapest fare class). You earn all Medallion bonuses.

So if you were Diamond, you earn 120% bonus of the base miles calculated. So the 30% T fare earns 66% RDM. If you have the option of upfaring to V (which earns 50%), I would do that if the costs are marginal, because V earns 50% base and therefore 110% of miles flown. The math benefits you.

Skyteam Elite Plus Benefits:

On-board welcome: I would say maybe 10% of flights as a Skyteam Elite Plus (Gold or higher Medallion) you would get greeted on board similar to how they treat their own golds. The majority of the time this does not happen.

Seat assignments: no benefits at all. You still have to pay for preferred seats, otherwise you are limited to the same general seat selection as all other fliers. Gate agents/check in agents may have some lee way but nothing is guaranteed. The system will also auto assign you like general pax (including middle seats) you must must must check with an agent for preferred seating.

Lounge access: you get access to the ever-so-crowded business class lounge at PVG. It's definitely above average for China, in my opinion, but may fall short of your expectations if you compare it to DL Sky Clubs or the nicer AF lounges. Only China Eastern Platinums get access to the First Class lounge section. When at out-stations, be careful: if you are flying economy and hold status, they will by default give you the worst lounge. Business/First pax get the invitation to the nicer lounge. For example, at JFK you will be given an invitation to the Alitalia lounge, despite being able to access both Korean and Air France as STE+. (Which is not saying much, since both of those lounges are crappy Priority Pass lounges, but still better than Alitalia.)

Priority boarding/check-in: No issues here, but I find for check-in desks rarely is status ever enforced. Multiple times I was checked in normally despite my number not being on the reservation, and then having to go back to have them add it in. What is the point of a business class counter if anybody can sneak in?

Free/op upgrades: Don't count on it. It rarely, if ever, happens. You can purchase it at the airport, but I don't know the cost. It's also possible to buy on board via the IFE, but the price was outrageous.

On board experience:

Smoking: yes, they do it. Either the pax, or the crew, or the pilots, for about 30-40% of my flights there were phases of the flights where you can smell smoke.

No cell phones: All Mainland Chinese carriers ban pax from using cell phones in-flight, even in airplane mode. It becomes a game of cat and mouse with the cabin crew if you really are desperate to use your phone.

Amenity kits (in Y): none. Blankets and pillows are provided for long-hauls. Intra-asia only gets blankets, with some pillows by request.

Wifi: it's available on most long-haul flights. And it's FREE. You can preregister or just do it on board, I have never seen the free code limit reached. It's also tied to your ID and Seat Number, so you need both these things handy, and be careful if you have switched seats. Also only one device can be signed in. Use your laptop or tablet, obviously. It's also slower than Gogo, in my experience. Oh, and it's censored because it goes through the Chinese Great Firewall. So make sure you have a VPN if you need to access Facebook, Twitter, Google, etc.

Food: it's average, if you like Chinese food. The selections are always both meat options, so if you are vegetarian you MUST pre-order or simply starve. If you have Western tastes, you may not particularly enjoy the meals because it's usually a selection between rice or noodles. There is also not much of sides (dessert, salad) either. You may want to bring snacks. The nice thing is that they serve two hot meals for long haul.

Drink: purely awful. Chinese red wine, or Tsingtao beer. No spirits. And even the soft drink selection is limited. They also do not give you personal bottled water on board other than what comes with your meal.

Service: surprisingly decent. They will disappear throughout the night as with most long-haul flights but they will always get you what you request. In my opinion, they are extremely patient and understanding.

Announcements: annoying as all hell. PIlots seem to either leave the seatbelt sign on all flight, and flash it when there's turbulence, and everytime they do that, the crew is forced to make an announcement. When this happens, all the screens on board light up brightly and wake up everybody up, in addition to the announcement.

Other pax: sometimes a problem. Have had several flights with old Chinese folks stay up all night chatting very loudly. One flight a young blonde backpacker girl also snuck into J, and the crew just let her do that. If you also are blessed to have an empty row on your flight, defend it! People will try to sit down on the other end and move around a lot.

IFE: acceptable. not that much worse than Delta Studio in terms of selection, but still OK if you fly them just once or twice.