I used to work in a call centre for Geek Squad, and did the over-the-phone work that Warrior mentioned. I never received many complaints about the quality of the service, other than more often than not, the field agent would just use very rudimentary steps to resolve computer issues (like reformatting a computer for almost any error, without trying other solutions, or simply installing a free antivirus to remove a virus, and charging $249 for the work).
That's basically the main thing I took away from working for them: they are way overpriced for the methods they use. You're always more likely to find someone you know who can offer the same services Geek Squad does, for a fraction of the cost (or nothing, if they're your friends). Geek Squad will likely get the job done for whatever issue you face, but for simpler issues it's best to look elsewhere.