When Buffett bought Berkshire Hathaway a few years after closing the partnership, his investment philosophy had changed. Your best bet to understand his investing is to simply read his letters.
He may come across as a bit folksy or country bumpkin, but he's fairly clear in his methodology.
Here are some links you may find helpful: http://www.rbcpa.com/WEB_letters/WEB_Letters_pre_berkshire.h...
http://www.berkshirehathaway.com/letters/letters.html
Enjoy.