Pros
I was with Simply Business a long time and feel lucky to have spent that time with them. Of all companies I have worked at, they are by far the most open to trying and learning new things. This fearlessness of change and improvement has put the company streets ahead of other companies who claim to be Agile. Simply Business have nailed actually being Agile, and additionally there's a great culture of doing things through Lean processes. What they have really nailed well, is being composed of multiple small teams all focussed around a particular objective, and each those teams being composed of a member of each part of the business. This means that all parts of the business are engaged and accountable to their team, help each other out and are much more easily able to empathise with the constraints of each others role and accordingly work together with those constraints. This is a whole different world from other companies which are simply split by department - with a 'business' side and a 'tech' side in which nobody truly understands each others constraints and just ends up in inefficiency and conflict. Simply Business put a great deal of effort into ensuring that anybody can voice their opinion and help steer the direction of the company. Whether you have positive or negative feedback, you feel comfortable to speak it - regardless of whether you're in a small team meeting or one of the big regular all-company meetings. It was easy to take inspiration from senior management, and their genuine drive to shake things up for the better in what has traditionally been a complacent industry with a lack of customer focus.
Cons
I agree with one of the other reviews that space is an issue, as the company has grown so quickly it can be very difficult to get usage of a meeting room, and there's not much lunchtime / recreational space without being a distraction to people not currently taking lunch / downtime.