60 Minutes produced some 1970s documents that reflect poorly on Bush's service. Are they fake? Some people think so. The memos are printed with proportional fonts. These are standard in word processors but were rare in typewriters in the early 1970s. I saw one of these typewriters used once and it was very difficult to get anything to print where you wanted it to. That's why mono-spaced typewriters were the norm.
Check the service documents available on Kerry's web site. All of them are mono-spaced.
Also, you had to have a special key for the raised "th". Few typewriters had this.
Little Green Footballs tried typing the document in MS Word using the Times New Roman font. The documents match. Look at the documents in the link. Notice that the last characters end at the same place between the two documents. This is significant since this will not happen if the fonts are even slightly different.
Also, Powerline has a sample of Killian's signature pasted beside the signature from one of the 60 Minutes documents. They are not very similar. The "K" is verry different and, in the verified signature it is the same height as the other letters. In the 60 Minutes document the "K" is huge. Also the "i" is very distinctive in the verified signature, almost like an inverted "V".
Then there is this analysis of the font by an expert. He's 90% sure that it is a fake.