I don't know how many times the question comes up about the install base of Flash on browsers, so here we go.

As of June 2004:

Flash 6 was at 94.1% in US, 96.4% in Europe and 92.4% in Asia.

Flash 7 was US 66.7%, Europe 81% and Asia 76.9%.  Growth seems healthy: In March 2004 these numbers were 52.5%, 59.9%, and 58.7 respectively.

The above data comes from NPD Online Research.  From their methodology statement:

"The survey presented respondents with several pages, each with an in line image in a different format on each page, and asked respondents to indicate whether or not they could see each of the images. This study was conducted via the World Wide Web, utilizing the NPD Online panel.

2,000 participants, comprising a representative Internet sample responded to this survey. The study was evaluated at a 95% significance confidence level, (5% risk)."

(Via Ape)