Pros
Working as a member of the Geek Squad is a good entry level IT position. You will have the opportunity to learn about desktop support, non-enterprise networking, customer service, and the business side of IT. The experience is especially useful if you are working at Geek Squad along with studying as a network professional, developer, or other IT field. Others working alongside you will usually also be looking to get experience and move on to other careers. You also have some career people who are either looking to get into retail management or are happy where they are. Overall it's a good way to get out there and start getting your feet wet.
Cons
Being primarily a retailer, Best Buy can often be a source of frustration for Geek Squad employees. General Managers at the store level usually put employees on a career path within the company at the services manager position, which usually means your manager will know a lot about retail and not much about IT or the service field. Add to that your manager is likely going to be very motivated to get business results from this position in an effort to use the services manager position as a stepping stone to greater things. As a result, you can expect some struggles with your manager, who will likely approach everything the same way they would if you were selling dishwashers.