A couple of things - I own a single share of BRK-B. My motivation for buying it was to one day take advantage of the shareholder privilege to attend the annual meeting in Omaha. Unfortunately, that has conflicted with my final exams for the past several years. However, I should be done with school in 2008, and might attend then. I have seen Buffett speak and highly recommend it if you ever have the opportunity.
I know that BRK owns a lot of different companies (and a large horde of cash, which is kind of like owning bonds), but personally, I sleep better at night having the bulk of my long-term investments in low-cost mutual funds from Fidelity and Vanguard.