Politics is strangling the entire company, but especially notable in engineering. Some senior leaders disagree with each other so much that they refuse to work together.
Some great engineers - some of the best in the industry - but few if any competent engineering managers. Again, relates to politics above. Engineering managers tend to be either ineffectual or toxic.
Career direction and growth is the biggest negative - there is none, and this is related to politics above. If a senior leader likes you, your career will go places. If not, they will lie to your face, tell you that there are no opportunities available in the team that you want to join, and then continue to hire for that team.
They used to allow people to move around, but it looks like this is being stopped. Last year I was told that engineers needed to stay in one engineering team for 3 months before being allowed to request a move. 3 months later, I was told that the deal had changed, and now staying in a team was expected to be permanent, with few exceptions. Combined with the fact that you can be reassigned to a new team, without being consulted first, and then be unable to request a move, its a recipe for disaster. Again, combined with politics above, means, if you are considering joining R3, you better hope you get lucky. If you get lucky and join a great team, you'll love it. If not, you'll hate it. Important: don't accept an offer unless you like the team you are going into, and don't accept an offer if they don't tell you what team it is.
Don't stay at R3 longer than 2 years - your salary growth will stagnate. I've now been at R3 and am looking to leave, and every recruiter that I've spoken to says I can get a 30% raise. Not 5%, not 10%, but 30%. That is how underpaid I am, and this is just after the raise cycles. Look what the Chief People Officer says about this, on this very website: "Unfortunately, 10% pay increases every year are not feasible based on our view of the industry". This quote is from another review on this website. Not "we pay people what they are worth". Not "we look after our best performers". Just we won't give you the pay increases that you deserve, and you have to go elsewhere to get them.
In summary: join R3 if you have between 0 and 5 years of experience. Stay for 2 years. You'll learn a lot, and you will be worth a lot more after that. Just don't expect this to be a 5 year company - not only is there no career growth, but there is no salary growth either.
I am on my way out and cannot wait to be out.