Pros
There are some great people working here and there are some great opportunities for getting into an industry that normally wouldn't hire you directly. They go out of their way to market anyone to their clients, with only vague regard to experience and skill level. Also, if your contract ends and you get put on the bench, they seem to have a very high tolerance for keeping you on the bench (whereas most other staffing agencies would just let you go immediately).
Cons
Where to begin. First of all, this is a staffing agency. They will try to convince you that they're not, and I'm not 100% sure they're even aware of the fact that they are one, but if you take a job at Sigma Connectivity, you will be taking a job at one of their clients, and Sigma will take a cut of your pay. At least that's how it is in the US (it might work differently in other countries Sigma operates in). This would be fine if they didn't try to operate as a "legit" company with their own offices and meetings and business trips, adding a massive amount of overhead, which they have to cover with the margin they're taking out of your pay as a contractor. They try everything they can to function as a "legit" company, which means no remote work (since they wouldn't have an excuse to have offices otherwise), and pointless meetings with your Sigma manager who has no idea what you're working on as a contractor for the client. They also have a bunch of catchy slogans such as "never work alone" even though the employees literally work alone 100% of the time since they're just contracted to various clients. They boast how open and transparent the company is, but nobody in management seems capable of giving a straight answer or commit to anything. That being said, the pay rate is not bad (make sure to negotiate beforehand and know what you're worth because they WILL take advantage of you if you don't - ESPECIALLY if you're on a visa since they know you're stuck) and their clients are some of the top tech companies around, so as long as you're aware of what this company actually is and you're fine with it, it's not a terrible place to be. Just take everything they say with a grain of salt because they WILL tell you anything you want to hear in order to get you on board, and they WON'T hold their promise (I was hired for a "hybrid" position - it wasn't hybrid even for a single day).