Pros
I've worked in small companies with a great atmosphere but rubbish processes, and large companies with great processes and rubbish atmosphere; but Deliveroo blends both of these positives together. Tech is treated as a first-class citizen and engineer voices are never ignored. The performance review process is transparent and everyone takes it seriously, dedicating time to ensure it's useful. There's also a healthy level of pragmatism amongst developers. Also rather nice is the agreement of "the right tool for the right job" no matter the financial cost; if the correct AWS product to use costs quite a bit, that's absolutely fine as long as it's the right choice - no penny-pinching there!
Cons
Career progression above Senior is very tied to your impact on the wider company outside your team, which can become quite time-consuming.