Pros
Of all the Big 4 accounting firms Deloitte has the best work life balance and the most committment to true diversity. Although in any job there will be people you will not want to work with I believe Deloitte has the best variety of people to choose from. Deloitte has a deep committment to learning within it's organization and if you are willing to work hard there is no limit to where your career can go. Flexibility is the name of the game. Deloitte's mentorship program is excellent with each new staff being paired with someone close to their own level as a "buddy" as well as a counselor who is generally a manager or above to help guide your career path and be a champion for you in the office.
Cons
The downsides to working at D&T are the same as working at any of the Big 4 accounting firms. They are public accounting firms. The hours during busy season are going to be terrible, but it's the nature of the beast. Also, becuase the industry is client driven things are seldom routine. Whereas in some other fields you have standard deadlines things change very rapidly in public. This can be both good and bad. Deloitte is notorious for promoting people who are technically competent but lack managerial skills. This would probably be the biggest downside to working there. Some of the managers are GREAT...others are not. Again, I would think this is true throughout the industry though.