Most analysis consists of figuring the mean and standard deviation, and checking the data for validity. Summarize the preference data you've collected. By observing the user's actions, and recording the user's opinions, either during the test using a thinking-aloud protocol or asking questions, or before and after the test in the questionaires, you have amassed a large set of preference data. Most questionaire designs allow you to quantify opinions using numerical scales, and the quantitative data found thusly can be analyzed using statistics much as the raw performance data. You can also summarize this data by selecting quotes from the subjects to highlight in the report as soundbites.
Usability testing is used throughout the product development lifecycle.
In early stages of product development, testing the previous version or competitors' products gives the design team benchmarks to shoot for in the design. In middle stages of development, testing validates the design and provides feedback with which to refine the design. At the later stages, testing ensures that the product meets the design objectives. Well, times do change. They DON'T require a Video Toaster, unless that's what's under the hood of the mix board in my lab now.