Interactive Flash-based websites (as opposed to the much simpler graphic-based ones) can be effective in some aspects, but in other ways, can be potentially hindering.
Flash websites can be very pretty, fun and professional-looking if done well, and can make the users' experience on your website a memorable one. What better way to advertise your business than with a highly technical, interesting and good-looking website?
Whilst bearing this in mind, however, Flash-based sites can often be confusing, complicated or misleading, with too much focus on the design and "look" of the site as opposed to its content or practicality, which can drive away potential customers. Worse still, the user may be unable to view the site at all; they may not have Flash installed or may be running an older operating system/browser, in which modern Flash scripts cannot be displayed correctly.
There are both upsides and downsides to using Flash on a website - an alternative is to go for both: a Flash-based website with all the snazzy features you can think of, and for those users who prefer the simpler side of the internet, a basic HTML and text-based website can be developed alongside. Why not have the best of both worlds? However, by far the easier, more compatible and more user-friendly option would be a graphics-based website with consideration for both ends of the opinion-spectrum.