Pros:

• This is really a great app not only for athletetic individuals but also for those who want to improve their physical activities. The way I see it, Strava really pushes you beyond limits by being motivated.
• You can already access relevant data to help you assess your previous physical activities
• This will make exercise more challenging since you can compete or get access to your friends' physical activities

Cons:

• I see no cons for this since this is also a FREE app.