Pros
You go through a big big volume of work in a short period of time - earn your chops, so to speak. The demands of work definitely provide a real learning experience that can prepare you for other roles and other challenges if you pay attention and realize you are learning. Excellent theories on leadership, personal development and coaching - though there is a walk-the-walk, talk-the-talk gap with many leaders so actual experiences will vary - the academics of it are great and if you can access them and absorb them, take them away for sure.
Cons
There is a built in blinder to cultures and benefits of working in other companies and in other industries. Pay is definitely lower than similar titles and similar roles in other organizations, work is much longer, more demanding, and much MUCH less balanced than similar roles and similar pay bands at other locations. Keeping a fresh out of school workforce helps maintain a veil around what other industries do and how their employees experience balance. Learning now as well that lots of other companies do not look well on the experience of working in telco - either come for a short time and get out, or expect to spend a looooong time in telco - either TELUS, its competitors, or one of the broader supporting companies. Career growth and opportunities (pay and titles raises) come ~to a point~ and plateau at 1st level manager for most. Development after that is almost always lateral moves and very very rarely up. (Unless you are in "the club").