Pros
Teladoc is a rare example of a large corporation (with the stability and resources of a large corporation) that is agile and fast-moving like a much smaller company. I joined Teladoc through a merger of a startup they acquired, so I expected very little, and was anticipating the "red tape" I experienced with big corps in the past. To my surprise, the company turned to be very open, practical, and transparent. The management is not afraid to experiment, make mistakes, admit mistakes, and change course when needed. It's certainly a great opportunity for anyone who wants to be heard and to be able to have an impact on a huge scale.
Cons
There's a significant amount of people who don't work in the main office (or in any of their offices). This can make teamwork and collaboration hard at times.