Pros
UST has many contracts and positions available globally, which can lead to consistent employment and allow for acquisition of skills relevant in the tech industry. This allows for one to explore different areas, which is most useful if you are an entry-level candidate. This can make for a great work-life balance, but it entirely depends on which client/project you work for.
Cons
Working directly with major clients, you may become aware that you could be paid much higher if you network properly and build relationships inside of that position - this describes a problem with genuine career growth from the start. Many contractors these days have a non-compete agreement which can potentially bar you from those roles and lock you in unless you're off of the project for 30-90 days. Incentive to achieve meaningful results may appear limited to many employees, so few individuals will actually go "above-and-beyond".