Pros
Most of my coworkers were good at their jobs and were fun people to be around. Sometimes the projects were genuinely interesting. Occasional free food and fun events. If, on its face, your job offer from GLG is the most attractive one you have, it may be the right choice to accept. See Cons for considerations though.
Cons
In the months before I left, Paul Todd & Friends increasingly seemed to have no idea what direction they were steering the company in (I imagine this was at least partially induced by a growingly impatient SFW, the private equity firm that owns a big share of GLG). Several great people (some hired very recently) got laid off for no coherent reason other than that GLG did a terrible job of budget planning. This was the worst that things got, but for over a year leading up to the layoffs there was constant vacillation by upper management about what should be prioritized and who should be responsible for it. This repeatedly led to many weeks' worth of work being abandoned or progress being indefinitely delayed, so it repeatedly felt like nothing was getting done in spite of people constantly grinding. A consistent complaint among new hires was that their jobs wound up being quite different from what they understood them to be before they started. This is at least partially due to the above. GLG espouses a commitment to development, but my reality was much rockier. Because of upper management's inconsistency, the skill I feel like I developed most in my years here was how to placate multiple exasperated managers who each want to take things in a different direction and don't understand why progress isn't being made. Pay and benefits are average - they're better if you work at a real tech company. GLG may have consistent strong growth each year, but unless you're really high up the chain, you'll get no spoils from GLG's success (bonuses are totally based on your own metrics and ratings from your manager; there's no equity compensation nor profit-sharing). This, along with a long promotion/raise curve, saps the motivation to stick things out when the going gets tough.