In 2021 it has been the cheapest airline flying to/from Russia. They have a very decent level of service. And I like their flexibility in booking and adding features. Customer support is always there for you in the chat.

Normally I wouldn't expect much from a budget airline, however I was pleasantly surprised from the moment I stepped into the airplane. The flight attendant Dmitriy approached me straight away offering his assistance in taking care of my hand luggage and escorting me to my seat (and I flew in economy, not business class!). Throughout the journey, the whole crew was very attentive, responsive, patient, polite and friendly. They were helpful and willing to go extra mile with a smile on their faces. I haven't seen this kind of dedication even in Qatar airways, which have been my favourite so far.
The aircraft itself was small, but clean. Nothing remarkable, just standard. But the crew does make the difference, each and every team member. Kudos to them and the management that trains and motivates them properly!
The only disappointing thing was that there was no notification of the flight delay, so I had to spend another 2.5 hours waiting at the airport. However this might have happened due to the fact that I booked my flight via the third party, so I cannot really blame the airline.

I am a US citizen married to a Russian national. We planned a summer 2021 family adventure including 8 people, me my wife and 6 of her Russian relatives. Trip included roundtrip airfare from Saint Petersburg to Novosibirsk. On the return flight my wife's sister and her 17 year old son were denied boarding due to an oversold flight and treated extremely poorly. They were taken for a 1 hour drive far outside the city to cheap accomodations, and the only food provided during their 20 hour delay was a dry sandwich, roll and low end pastry. Nothing to drink. When my wife's sister asked for more food for her son she was denied. What inappropriate behavior by S7 and their employees.

The secret to get outstanding service on S7 is so simple!
Prior to flying
I had learnt basic Russian from YouTube "learn Russian while you sleep"
The moment flight attendants heard me speaking Russian, they were super friendly and attentive to my needs.
Food is good but don't expect fine cuisine .
The advantage of the business class cabin is the people you meet... such as a champion wrestler and a KHL's ice hockey star player !
Conclusion: learn a little Russian before you fly S7 and a new world will open to you !

I used to fly S7 regularly before covid and first time too it after COVID. They were decent airline with good quality, almost always on schedule. My flight was delayed by over 30 min without any announcement and nobody present at the gate to advise passengers how long to wait. Finally, they started onboarding everyone. Apparently, due to cost optimizations, they stopped using air conditioners when they onboard passengers. It was 35C on board when we entered and we were waiting for a take off for over 30 min in this mode. Stewardess was helpless in providing any information. The airplane was also like 30 years old with passenger seats condensed to maximum degree. It is more like a low cost airline experience those their pricing 2-3x times higher. Totally opting out from their service.