Pros
As all the other reviews have said, there is a great culture among the team - everyone is very warm and supportive, and do really have a “go together” attitude. Mentoring and personal development is given a lot of focus and treated well. They're also very positive, driven and entrepreneurial. The work, in proposition design (design sprints for ideating, testing and developing new ideas for businesses) can be quite interesting, and is certainly more creative and agile than your standard management-consulting work. While they easy to see as stuffy and boring, Deloitte do look after their people quite well. The pay/benefits are decent (probably better than most small agencies), you don't get messed around too much, there are flexible working options, and opportunities to move around the organisation if something else catches your interest. International travel and placements aren't impossible, but they're easier for higher level people.
Cons
I’ll write primarily about my experience as a designer, although as other people have hinted there have been some other organisational challenges since the Deloitte acquisition. Any prospective new designers for Market Gravity should be aware that while the company likes to talk a big game about "building" and "making things real", the core work is typically done at the very early concepting stage of the design process. As such your work will generally involve quickly turning around communications of concepts - usually graphic design, slide design, video editing, and some rough prototyping. MG are rarely involved in developing the concept through to delivery, and so if you are hoping to do deep UX/UI design and take products through into the hands of users you will probably be disappointed. However there is the opportunity to move across the organisation into Deloitte Digital, where you’ll get to work on more 'real' design. It was a good place to start my career, I got exposure to a range of interesting strategic projects, and design thinking methods that you might not get to play with as much in a more typical agency or web-dev house. However there is a limit to the depth of industry skills and design experience you can develop, and after a while you’ll reach a point where you have to decide between moving fully into consulting and innovation strategy, or moving elsewhere if you want to do more applied design work. As for the current state of the MG, I’d say they’ve been through a fairly prolonged identity crisis as a result of the Deloitte acquisition (I think this is quite common for agencies that get acquired by the big 4). They’ve explored various strategic avenues, had a few phases of people-churn, but seem to be possibly turning a corner and getting ready for a new start. It’s been a tough few years for them trying to figure out how they fit into the wider scheme of things, and they still haven’t nailed it, although I suppose that does possibly give an opportunity for ambitious people to propose new ideas. Also be aware: the company had a painful shift into the slower Deloitte programme for progression and promotion. The review cycle is now once-yearly, although in practice this means basically two-yearly for a shot at moving up.