Pros
I joined Berkeley after 7 years in a Big-4 consultancy on the promise of being able to lead challenging projects at major businesses. From the outset I've had the opportunity to be stretched and developed at what feels like a much greater rate than at my previous firm. The lack of hierarchy, and corresponding ownership you take of the projects from day 1, gives you room to shape, own and drive the right outcomes that are needed for the client. In the past three years, I've presented to Cabinet Ministers, led multi-million pound projects and helped shape the commercial strategies of more than one household name. At my previous firm, I might have been one of a number on the team; here I've found myself much more readily in the hot-seat. As a result, I feel my skill-set, experience and confidence has grown significantly. And this has all been achieved with better work-life balance (I am in control); better pay with more regular recognition for achievement; very little internal politics or pressure to jump through promotion hoops (as there aren't any); and all the while developing some good mates and most importantly: having fun. It is a personality-driven business that thrives on us all getting along with each other - the partners realise this and actively promote the social stuff. If I was ever to move from Berkeley, I very much doubt I'd ever move into another consulting business (definitely not back into the Big-4). I don't think the mix of quality, balance, remuneration and fun can be bettered.
Cons
As a small firm, there are only a small number of roles that are likely to be available when you roll off a project; there is therefore a risk that you could end up working on something you don't have a big interest, or level of expertise in. Whilst this could be seen as a negative, it also presents an opportunity to develop new skills and experience, and to broaden out your CV. In my three years, I've only been involved in what I would consider 'decent' projects (eg commercial or business strategy development), and as with all consulting jobs there are ways of "creating your own luck" (ie doing good work for an interesting client invariably leads to more interesting work...). If you are resourced onto something 'new', then there is every chance that someone else in the firm has done it before - requests for help are nearly always followed up with practical, helpful advice. And with your listening partner never far away from the content, they're able to step in more directly to help if need be too. As a firm with a strong, but not very well known brand, we do not carry the same weight or kudos with clients who are not familiar with us. We can appear expensive as a result (especially when considering the absence of any junior grades to leverage our rates) - and that can create challenges in terms of procurement. The vast majority of our work comes, however, from referral and from clients who seek us out for the experience and value we can provide.