Vantaggi
It's great to work for such a storied British institution. While we may make fun of the zealous nature of the readership every so often, it's great to be creating a product for such a passionate and enthusiastic audience. The work is fairly interesting, providing you're on a product area you can relate to, and it's always enjoyable talking with other colleagues about the various issues you've encountered and how to solve them. It's all set in a decent office in a wonderful location, there is working from home allowed, and you get a good quantity of annual leave. It's also very rare to find a job that's a genuine 9-5 these days - getting home every evening while so many others would still be at work is priceless. Despite having left the company some time ago, I'm still friends with people I worked with at Which? to this day.
Svantaggi
I'm largely going to echo what you've read in other reviews here. Which? is grossly mismanaged. It's natural at a company this size I suppose, but it was incredibly depressing watching talented, honest, hard-working colleagues get ground into the dirt as time passed by. Workloads are heavy and repetitive. Salaries are at or below the industry standard. When confronted on this the company stated that pay is checked against 'comparable roles' across the market. Why a company that prides itself on being the foremost in its field thinks it's acceptable to underpay its employees, all while demanding top-class performance, escapes me. There's a lot of decisions like that at Which?. Higher-ups are paranoid and untrusting. A rigid corporate structure means that those who ascend to the upper ranks are virtually untouchable, yet they still feel the need to manipulate their underlings and play favourites as if they could come for their job at any moment. Micromanagement is commonplace and your progression is almost entirely dictated by how your seniors are feeling on any given day. Change is resisted at every turn. Hot desking is an exercise in frustration (and spreading germs).