We are considering using a template which includes a Flash
introduction and would like to know what percentage of Internet users
would be able to view it.  Also, for those who cannot - what would
they see?

The most recent figures I've found indicate that at least 98% of users
can view Flash:

"Macromedia Flash is defacto web animation standard. Currently more
than 98% of web users in the U.S. are able to view flash content (NPD
Research browser survey, December 2001). It comes bundled with all
major operating systems and browsers on the market."

Just Go There: MACROMEDIA FLASH DESIGN
http://justgothere.com/macromedia_flash_animation.htm

"Macromedia claims 98 percent of online users are able to view Flash
content. That would make it perhaps the most successful browser add-on
ever."

Internet Week: Macromedia Hopes For Bigger Flash Role 
http://www.internetweek.com/story/INW20020304S0006

"Flash is the leading tool to create rich Internet content and
applications, with more than 98 percent of online users able to view
Flash content today across leading platforms and devices. More than
two million online users download a Flash Player every day."

Webventor: Flash
http://www.webventor.com/multimedia/flashpage.htm 

To handle the few users who do not have Flash capability, most sites
that use Flash have a provision that either offers options to redirect
the user to an alternate page or to download the appropriate plug-in
that will enable the user to view Flash. Here are some examples:

Father's Love Letter (see options at bottom of page)
http://www.fathersloveletter.com/fllpreviewlarge.html

The Secret Books
http://www.thesecretbooks.com/secret_java.html

Borneo Connections
http://www.mega-ecom.com/borneoconnections/

Google search strategy:

Google Web Search: "able to view flash" + "percent"
://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=%22able+to+view+flash%22+percent

I hope this information is useful. If anything is unclear, or if a
link does not function, please request clarification; I'll be glad to
offer further assistance before you rate my answer.

Best regards,
pinkfreud

Thanks!