Pros
Fixing computers and helping people provides a good deal of satisfaction. I learned a lot about different vulnerabilities, part failure rates, manufacturing costs and build quality of products. Depending on where you work, having good co-workers also makes it a very enjoyable experience if you've got an interest in technology.
Cons
At the location I worked at, there were a lot of customers who came in screaming from the get-go, and to be fair, the prices that Geeksquad wants to charge people are sometimes a little ridiculous. Even getting customers to agree to charges, we'd have them come back later and start a shouting match until a manager came and gave them the service at an extreme discount. This prompted more yelling in future visits and an expectation of savings due to getting special treatment the first time.