Some great people but...
Pros
A lot of people at PLOS were genuinely interested in the 'mission' and friendly to work with. Particularly at the lower levels, people were willing to work very hard and go over and above. Pay is ok for publishing, although even the lowest level of worker has a lot of responsibility and a high workload.
Cons
Minimal opportunity for progression, particularly in the UK office. Most people picked to become managers are young and completely inexperienced in management - barely out of university. No decent training to address this and this has been cut further recently. Promotions at times seemed random and unfair. Very high turnover with no obvious effort by higher management to address the reasons - perhaps preferring to hire new grads who would be cheaper and tow the line without questions. So many good people have left - this is the company's loss and could well be their downfall. Don't even think about working here if you expect 21st Century HR policies (i.e. any kind of flexible working). In this respect they are living in the dark ages, much to their own detriment.