Pros
If you enjoy drinking there is free beer every Friday and at times we have stayed until the early hours of Saturday morning. There has also at times been free dinner provided if you are prepared to stay late. You are given a reasonably high level of autonomy almost from day one. They will hire you whatever your skill level. I know of quite a few colleagues who have gone on to much better roles having started at Obsidian so if you can handle a couple of years it can be a good stepping stone. Since they have the backing of a pension fund they are probably a fairly secure place to work and getting fired is almost unheard of.
Cons
During the past 2 years I have seen Obsidian grow a lot, but the company is still ran like a small business - and not in a good way. The pay at Obsidian is definitely below market rates, you will start somewhere under 30k and even managers are on less than 55k. Student workers are paid less than 20k which I honestly think is outrageous considering how poorly they are treated and the hours they are expected to work. They rely on hiring the weaker applicants which other companies didn't pick. I can speak from experience that after failing to get a job elsewhere due to doing the wrong degree and lacking any experiences - Obsidian were my last chance and luckily they did hire me. The progression is poor, even after 2 years I am still on below what my friends at other agencies make and they have far more benefits like pension, company phone and a Macbook. This is obvious from the fact that the turnover at Obsidian is very high once people have got their first 18 months out of the way. There is rampant nepotism - a recent round of promotions and raises showed the companies true colors. One person was promoted far earlier than is usual and no questions were asked despite it being well known that they're dating their manager. Pay rises to even match inflation were also nowhere to be seen, I have friends working for other similar companies who have been given bonuses and generous raises but we were given almost nothing. The selection of clients Obsidian have is a mixture of a small number of medium sizes companies which are generally new to the market and then the majority is made up of small webshops. Which clients you get given really effects how you will progress technically and whilst I believe I've been trying my best I know even the managers don't have the same technical skills which you will get taught at other more successful agencies and this can be limiting. Perhaps the worst part of Obsidian is the constant bullying and lack of compassion both from colleagues and managers. Over the two years I have worked at Obsidian I have seen one mass resignation of 5+ people which led to the formation of a competitor, at least 10 people go down with stress and multiple other people suddenly disappear without any explanation. This goes with being expected to work 50+ hours a week with no overtime pay and I know of colleagues who push closer to 70 hours a week and management make no effort to look out for them.