Decent place to be if you can get a full term contract.
Pros
The London office is brilliant compared to other places I've worked at; how could it not be with as many free cokes as you want and a roof terrace to look out over London with a bit of lunch? I've also found that if you really apply yourself there are opportunities to move on and up within the company - my initial contract was a third party, 6 month one and now I'm on a contract without a specified end date. I haven't come across any office bullies or anyone who's into being an spiteful/rude for the sake of it so far, which makes getting through the day fairly easy. The fact I can have my headphones in unless making phone calls helps, too.
Cons
When you work on content it can be frustrating that the company ethos is pretty fixed on the use of technology. Try to get some variation into the work you're doing or you'll hear every tick and tock from your watch. The main problem, though, is that anyone on a normal contract has to leave for at least 6 weeks after 2 years of continuous employment with the company. I think it's some sort of workaround for them to avoid having to give people full employees' rights, but whatever the reason they've lost a lot of good people because of it.