Pros
Company is truly one of the most innovative in research. It makes you proud and happy to work with tools that you can really believe in. The atmosphere is good, staff satisfaction is very high despite a few of the negative reviews here (they do staff satisfaction surveys and are VERY open with the results, warts and all). When there are issues, they confront them head on and senior managers really do their best to improve things. Staff turnover has typically been very low with many people working their way from bottom to top. Benefits are pretty good and they are quite casual (e.g. you can use your work phone for pretty much unlimited personal purposes). Recently they have been encouraging staff to take time back when they have had a particularly busy project - nice that it's give and take. You can learn a lot here with interesting work and talented staff. No time sheets is a major plus!
Cons
Growing pains have been felt over the years as it transitioned from a small start-up to a mid-sized agency. Communication between senior management and staff could be better. Sometimes they change course without explaining why. They try different things, when they don't work out it can be frustrating but I guess that's the price to pay for being an innovative company. They should have more transparency of salary bands. For some reason they don't like to share them with staff. HR are more an admin function and it's left to the account teams to do all the training, recruitment, improving work/life balance etc. You need to work hard at BrainJuicer so it's not a place if you just want to take it easy with minimal effort. On the positive side, you can get promoted pretty quickly if you're prepared to put in the effort.