Pros
As an intern, you can be given a lot of responsibility and opportunities to prove yourself. Also, upper-level employees are very supportive and willing to share career information and advice. One of the best features of the summer internship program is the speaker series, when various people from different magazines and positions within the company at large come and tell the inter class about their career paths, what's going on in the industry, and how to achieve what they've achieved. Another nice aspect of working at Time Inc seems to be that once you're within the company, it's fairly easy to move around between different brands.
Cons
This is the case in most of the magazine industry, but obviously the pay isn't amazing at the lower levels.