Pros
They genuinely care about people. More so than nearly every other place I've worked. It might not always filter down but there are a lot of discussions about looking after people, particularly in the department I work in. This has been especially evident during the Coronavirus outbreak. There is a huge amount of variety in terms of clients, projects, pitches - really good for getting experience. Back when the office was open - having dogs plodding around makes a surprisingly big difference to well-being (in my opinion). Great parties and events organised by a brilliant small team of people. Without them I don't think the culture would be as good. Genuine desire to embrace change and to improve. At all levels. This is quite rare. The people are really nice. Just a nice bunch of smart, friendly people who want to do a good job.
Cons
Actually enacting change has historically been quite difficult, for lots of reasons. Mainly due to habit, in my opinion. There is a bit of a legacy of top-down control which stifles autonomy to some extent. There can be a lack of empathy between certain teams which can cause tension - caused by commercial realities most often, but which could've been anticipated and mitigated earlier on. There is quite a lot of fire-fighting that goes on that is unnecessary if certain habits / behaviours are broken and replaced with better ones - but it requires people to stop and think and plan ahead better.