• usability3
• Stability8
• Installation10
• Functionality2
• Appearance6

Don't install it if you don't need it. Controls (e.g. pause, volume, stop) often don't work! Furthermore, you cannot (e.g. by right-clicking Flash content on a Web site) identify the source of unwanted content for the purpose of banning it from your computer. In fact, previous versions of Flash would sometimes but not always identify the source so you could ban an advertising site (or pornography if it ever came up) from your computer by using the HOSTS file, parental control, or whatever. With Flash 10, I have not been able to identify Web sites in this manner.